diff --git a/pkg/manifests/amcfg.go b/pkg/manifests/amcfg.go
index 7d2c6868e8..e4204db5e7 100644
--- a/pkg/manifests/amcfg.go
+++ b/pkg/manifests/amcfg.go
@@ -5,6 +5,7 @@ import (
 	"net/url"
 
 	"golang.org/x/net/http/httpproxy"
+	yaml2 "gopkg.in/yaml.v2"
 	v1 "k8s.io/api/core/v1"
 )
 
@@ -13,10 +14,19 @@ type PrometheusAdditionalAlertmanagerConfigs []AdditionalAlertmanagerConfig
 
 // MarshalYAML implements the yaml.Marshaler interface.
 func (a PrometheusAdditionalAlertmanagerConfigs) MarshalYAML() (interface{}, error) {
+	return a.MarshalYAMLWithTLSConfig(nil, "")
+}
+
+// MarshalYAMLWithTLSConfig marshals the configs with the provided TLS configuration
+func (a PrometheusAdditionalAlertmanagerConfigs) MarshalYAMLWithTLSConfig(cipherSuites []string, minTLSVersion string) (interface{}, error) {
 	result := make([]interface{}, len(a))
 
 	for i, item := range a {
-		promAmCfg := prometheusAdditionalAlertmanagerConfig(item)
+		promAmCfg := prometheusAdditionalAlertmanagerConfigWithTLS{
+			AdditionalAlertmanagerConfig: item,
+			CipherSuites:                 cipherSuites,
+			MinTLSVersion:                minTLSVersion,
+		}
 
 		y, err := promAmCfg.MarshalYAML()
 		if err != nil {
@@ -29,6 +39,20 @@ func (a PrometheusAdditionalAlertmanagerConfigs) MarshalYAML() (interface{}, err
 	return result, nil
 }
 
+// MarshalPrometheusAdditionalAlertmanagerConfigs marshals the configs with secure TLS settings
+func (f *Factory) MarshalPrometheusAdditionalAlertmanagerConfigs(amConfigs []AdditionalAlertmanagerConfig) ([]byte, error) {
+	prometheusAmConfigs := PrometheusAdditionalAlertmanagerConfigs(amConfigs)
+	cipherSuites := f.APIServerConfig.TLSCiphers()
+	minTLSVersion := f.APIServerConfig.MinTLSVersion()
+
+	result, err := prometheusAmConfigs.MarshalYAMLWithTLSConfig(cipherSuites, minTLSVersion)
+	if err != nil {
+		return nil, err
+	}
+
+	return yaml2.Marshal(result)
+}
+
 // amConfigPrometheus is our internal representation of the Prometheus alerting configuration.
 type amConfigPrometheus struct {
 	Scheme               string                  `yaml:"scheme,omitempty"`
@@ -46,26 +70,29 @@ type amConfigAuthorization struct {
 }
 
 type amConfigTLS struct {
-	CA                 string `yaml:"ca_file,omitempty"`
-	Cert               string `yaml:"cert_file,omitempty"`
-	Key                string `yaml:"key_file,omitempty"`
-	ServerName         string `yaml:"server_name,omitempty"`
-	InsecureSkipVerify bool   `yaml:"insecure_skip_verify,omitempty"`
+	CA                 string   `yaml:"ca_file,omitempty"`
+	Cert               string   `yaml:"cert_file,omitempty"`
+	Key                string   `yaml:"key_file,omitempty"`
+	ServerName         string   `yaml:"server_name,omitempty"`
+	InsecureSkipVerify bool     `yaml:"insecure_skip_verify,omitempty"`
+	MinVersion         string   `yaml:"min_version,omitempty"`
+	CipherSuites       []string `yaml:"cipher_suites,omitempty"`
 }
 
 type amConfigStaticConfigs struct {
 	Targets []string `yaml:"targets"`
 }
 
-// prometheusAdditionalAlertmanagerConfig is an AdditionalAlertmanagerConfig
-// which can be marshaled into a yaml string, compatible with the Prometheus
-// configuration format
-type prometheusAdditionalAlertmanagerConfig AdditionalAlertmanagerConfig
+// prometheusAdditionalAlertmanagerConfigWithTLS is an AdditionalAlertmanagerConfig
+// with TLS configuration that can be marshaled with secure cipher suites and min TLS version
+type prometheusAdditionalAlertmanagerConfigWithTLS struct {
+	AdditionalAlertmanagerConfig
+	CipherSuites  []string
+	MinTLSVersion string
+}
 
 // MarshalYAML implements the yaml.Marshaler interface.
-// It marshals a PrometheusAdditionalAlertmanagerConfig into a format
-// compatible with the Prometheus configuration.
-func (a prometheusAdditionalAlertmanagerConfig) MarshalYAML() (interface{}, error) {
+func (a prometheusAdditionalAlertmanagerConfigWithTLS) MarshalYAML() (interface{}, error) {
 	cfg := amConfigPrometheus{
 		Scheme:               a.Scheme,
 		PathPrefix:           a.PathPrefix,
@@ -84,6 +111,20 @@ func (a prometheusAdditionalAlertmanagerConfig) MarshalYAML() (interface{}, erro
 		},
 	}
 
+	// Check if this configuration needs TLS security settings
+	// Apply strict TLS only for HTTPS connections WITHOUT explicit TLS config
+	// If explicit TLS config is provided, respect user's choices
+	hasExplicitTLSConfig := a.TLSConfig.CA != nil || a.TLSConfig.Cert != nil || a.TLSConfig.Key != nil ||
+		a.TLSConfig.ServerName != "" || a.TLSConfig.InsecureSkipVerify
+
+	needsTLSSecuritySettings := a.Scheme == "https" && !hasExplicitTLSConfig
+
+	// Apply TLS security settings only for HTTPS connections without explicit TLS config
+	if needsTLSSecuritySettings {
+		cfg.TLSConfig.MinVersion = a.MinTLSVersion
+		cfg.TLSConfig.CipherSuites = a.CipherSuites
+	}
+
 	caPath, err := secretPath(a.TLSConfig.CA)
 	if err != nil {
 		return nil, err
@@ -141,6 +182,9 @@ type amHTTPConfig struct {
 func (f *Factory) ConvertToThanosAlertmanagerConfiguration(ta []AdditionalAlertmanagerConfig) ([]thanosAlertmanagerConfiguration, error) {
 	result := make([]thanosAlertmanagerConfiguration, len(ta))
 
+	cipherSuites := f.APIServerConfig.TLSCiphers()
+	minTLSVersion := f.APIServerConfig.MinTLSVersion()
+
 	for i, a := range ta {
 		cfg := thanosAlertmanagerConfiguration{
 			Scheme:     a.Scheme,
@@ -159,6 +203,20 @@ func (f *Factory) ConvertToThanosAlertmanagerConfiguration(ta []AdditionalAlertm
 			},
 		}
 
+		// Check if this configuration needs TLS security settings
+		// Apply strict TLS only for HTTPS connections WITHOUT explicit TLS config
+		// If explicit TLS config is provided, respect user's choices
+		hasExplicitTLSConfig := a.TLSConfig.CA != nil || a.TLSConfig.Cert != nil || a.TLSConfig.Key != nil ||
+			a.TLSConfig.ServerName != "" || a.TLSConfig.InsecureSkipVerify
+
+		needsTLSSecuritySettings := a.Scheme == "https" && !hasExplicitTLSConfig
+
+		// Apply TLS security settings only for HTTPS connections without explicit TLS config
+		if needsTLSSecuritySettings {
+			cfg.HTTPConfig.TLSConfig.MinVersion = minTLSVersion
+			cfg.HTTPConfig.TLSConfig.CipherSuites = cipherSuites
+		}
+
 		caPath, err := secretPath(a.TLSConfig.CA)
 		if err != nil {
 			return nil, err
diff --git a/pkg/manifests/manifests.go b/pkg/manifests/manifests.go
index 4e023c9346..30ac2637cc 100644
--- a/pkg/manifests/manifests.go
+++ b/pkg/manifests/manifests.go
@@ -1634,9 +1634,8 @@ func (f *Factory) setupPrometheusRemoteWriteProxy(p *monv1.Prometheus) {
 
 func (f *Factory) PrometheusK8sAdditionalAlertManagerConfigsSecret() (*v1.Secret, error) {
 	amConfigs := f.config.ClusterMonitoringConfiguration.PrometheusK8sConfig.AlertmanagerConfigs
-	prometheusAmConfigs := PrometheusAdditionalAlertmanagerConfigs(amConfigs)
 
-	config, err := yaml2.Marshal(prometheusAmConfigs)
+	config, err := f.MarshalPrometheusAdditionalAlertmanagerConfigs(amConfigs)
 	if err != nil {
 		return nil, err
 	}
@@ -1654,8 +1653,8 @@ func (f *Factory) PrometheusK8sAdditionalAlertManagerConfigsSecret() (*v1.Secret
 
 func (f *Factory) PrometheusUserWorkloadAdditionalAlertManagerConfigsSecret() (*v1.Secret, error) {
 	amConfigs := f.config.AdditionalAlertmanagerConfigsForPrometheusUserWorkload()
-	prometheusAmConfigs := PrometheusAdditionalAlertmanagerConfigs(amConfigs)
-	config, err := yaml2.Marshal(prometheusAmConfigs)
+
+	config, err := f.MarshalPrometheusAdditionalAlertmanagerConfigs(amConfigs)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/manifests/manifests_test.go b/pkg/manifests/manifests_test.go
index a6858f08d2..46591a013f 100644
--- a/pkg/manifests/manifests_test.go
+++ b/pkg/manifests/manifests_test.go
@@ -2058,6 +2058,20 @@ func TestPrometheusK8sAdditionalAlertManagerConfigsSecret(t *testing.T) {
   api_version: v2
   authorization:
     credentials_file: /etc/prometheus/secrets/alertmanager1-bearer-token/token
+  tls_config:
+    min_version: VersionTLS12
+    cipher_suites:
+    - TLS_AES_128_GCM_SHA256
+    - TLS_AES_256_GCM_SHA384
+    - TLS_CHACHA20_POLY1305_SHA256
+    - ECDHE-ECDSA-AES128-GCM-SHA256
+    - ECDHE-RSA-AES128-GCM-SHA256
+    - ECDHE-ECDSA-AES256-GCM-SHA384
+    - ECDHE-RSA-AES256-GCM-SHA384
+    - ECDHE-ECDSA-CHACHA20-POLY1305
+    - ECDHE-RSA-CHACHA20-POLY1305
+    - DHE-RSA-AES128-GCM-SHA256
+    - DHE-RSA-AES256-GCM-SHA384
   static_configs:
   - targets:
     - alertmanager1-remote.com
@@ -2353,6 +2367,21 @@ func TestThanosRulerAdditionalAlertManagerConfigsSecret(t *testing.T) {
 - scheme: https
   path_prefix: /path-prefix
   api_version: v2
+  http_config:
+    tls_config:
+      min_version: VersionTLS12
+      cipher_suites:
+      - TLS_AES_128_GCM_SHA256
+      - TLS_AES_256_GCM_SHA384
+      - TLS_CHACHA20_POLY1305_SHA256
+      - ECDHE-ECDSA-AES128-GCM-SHA256
+      - ECDHE-RSA-AES128-GCM-SHA256
+      - ECDHE-ECDSA-AES256-GCM-SHA384
+      - ECDHE-RSA-AES256-GCM-SHA384
+      - ECDHE-ECDSA-CHACHA20-POLY1305
+      - ECDHE-RSA-CHACHA20-POLY1305
+      - DHE-RSA-AES128-GCM-SHA256
+      - DHE-RSA-AES256-GCM-SHA384
   static_configs:
   - alertmanager1-remote.com
   - alertmanager1-remotex.com