diff --git a/cache.go b/cache.go
index 7270a258..cc177624 100644
--- a/cache.go
+++ b/cache.go
@@ -97,6 +97,7 @@ type decodingStructType struct {
 	fieldIndicesByIntKey map[int64]int  // Only populated if toArray is false
 	err                  error
 	toArray              bool
+	toIndefArray         bool
 }
 
 func getDecodingStructType(t reflect.Type) (*decodingStructType, error) {
@@ -111,9 +112,10 @@ func getDecodingStructType(t reflect.Type) (*decodingStructType, error) {
 	flds, structOptions := getFields(t)
 
 	toArray := hasToArrayOption(structOptions)
+	toIndefArray := hasToIndefArrayOption(structOptions)
 
-	if toArray {
-		return getDecodingStructToArrayType(t, flds)
+	if toArray || toIndefArray {
+		return getDecodingStructToArrayType(t, flds, toIndefArray)
 	}
 
 	fieldIndicesByName := make(map[string]int, len(flds))
@@ -163,7 +165,7 @@ func getDecodingStructType(t reflect.Type) (*decodingStructType, error) {
 	return structType, nil
 }
 
-func getDecodingStructToArrayType(t reflect.Type, flds fields) (*decodingStructType, error) {
+func getDecodingStructToArrayType(t reflect.Type, flds fields, toIndefArray bool) (*decodingStructType, error) {
 	decFlds := make(decodingFields, len(flds))
 	for i, f := range flds {
 		// nameAsInt is set in getFields() except for fields with an unparsable tagged name.
@@ -185,8 +187,9 @@ func getDecodingStructToArrayType(t reflect.Type, flds fields) (*decodingStructT
 	}
 
 	structType := &decodingStructType{
-		fields:  decFlds,
-		toArray: true,
+		fields:       decFlds,
+		toArray:      true,
+		toIndefArray: toIndefArray,
 	}
 	decodingStructTypeCache.Store(t, structType)
 	return structType, nil
@@ -199,6 +202,7 @@ type encodingStructType struct {
 	omitEmptyFieldsIdx []int          // Only populated if toArray is false
 	err                error
 	toArray            bool
+	toIndefArray       bool
 }
 
 func (st *encodingStructType) getFields(em *encMode) encodingFields {
@@ -258,6 +262,9 @@ func getEncodingStructType(t reflect.Type) (*encodingStructType, error) {
 
 	flds, structOptions := getFields(t)
 
+	if hasToIndefArrayOption(structOptions) {
+		return getEncodingStructToIndefArrayType(t, flds)
+	}
 	if hasToArrayOption(structOptions) {
 		return getEncodingStructToArrayType(t, flds)
 	}
@@ -354,6 +361,27 @@ func getEncodingStructType(t reflect.Type) (*encodingStructType, error) {
 	return structType, nil
 }
 
+func getEncodingStructToIndefArrayType(t reflect.Type, flds fields) (*encodingStructType, error) {
+	encFlds := make(encodingFields, len(flds))
+	for i, f := range flds {
+		encFlds[i] = &encodingField{field: *f}
+		encFlds[i].ef, encFlds[i].ief, encFlds[i].izf = getEncodeFunc(f.typ)
+		if encFlds[i].ef == nil {
+			structType := &encodingStructType{err: &UnsupportedTypeError{t}}
+			encodingStructTypeCache.Store(t, structType)
+			return nil, structType.err
+		}
+	}
+
+	structType := &encodingStructType{
+		fields:       encFlds,
+		toArray:      true,
+		toIndefArray: true,
+	}
+	encodingStructTypeCache.Store(t, structType)
+	return structType, nil
+}
+
 func getEncodingStructToArrayType(t reflect.Type, flds fields) (*encodingStructType, error) {
 	encFlds := make(encodingFields, len(flds))
 	for i, f := range flds {
@@ -398,3 +426,9 @@ func hasToArrayOption(tag string) bool {
 	idx := strings.Index(tag, s)
 	return idx >= 0 && (len(tag) == idx+len(s) || tag[idx+len(s)] == ',')
 }
+
+func hasToIndefArrayOption(tag string) bool {
+	s := ",toindefarray"
+	idx := strings.Index(tag, s)
+	return idx >= 0 && (len(tag) == idx+len(s) || tag[idx+len(s)] == ',')
+}
diff --git a/encode.go b/encode.go
index 0620bc63..97e1aa16 100644
--- a/encode.go
+++ b/encode.go
@@ -1480,6 +1480,47 @@ func putKeyValues(x *[]keyValue) {
 	keyValuePool.Put(x)
 }
 
+func encodeStructToIndefArray(e *bytes.Buffer, em *encMode, v reflect.Value) (err error) {
+	structType, err := getEncodingStructType(v.Type())
+	if err != nil {
+		return err
+	}
+
+	if b := em.encTagBytes(v.Type()); b != nil {
+		e.Write(b)
+	}
+
+	flds := structType.fields
+
+	// Write indefinite-length array header (0x9f)
+	e.WriteByte(cborArrayWithIndefiniteLengthHead)
+	for i := 0; i < len(flds); i++ {
+		f := flds[i]
+
+		var fv reflect.Value
+		if len(f.idx) == 1 {
+			fv = v.Field(f.idx[0])
+		} else {
+			// Get embedded field value.  No error is expected.
+			fv, _ = getFieldValue(v, f.idx, func(reflect.Value) (reflect.Value, error) {
+				// Write CBOR nil for null pointer to embedded struct
+				e.Write(cborNil)
+				return reflect.Value{}, nil
+			})
+			if !fv.IsValid() {
+				continue
+			}
+		}
+
+		if err := f.ef(e, em, fv); err != nil {
+			return err
+		}
+	}
+	// Write break code (0xff)
+	e.WriteByte(cborBreakFlag)
+	return nil
+}
+
 func encodeStructToArray(e *bytes.Buffer, em *encMode, v reflect.Value) (err error) {
 	structType, err := getEncodingStructType(v.Type())
 	if err != nil {
@@ -2079,6 +2120,9 @@ func getEncodeFuncInternal(t reflect.Type) (ef encodeFunc, ief isEmptyFunc, izf
 		if f, ok := t.FieldByName("_"); ok {
 			tag := f.Tag.Get("cbor")
 			if tag != "-" {
+				if hasToIndefArrayOption(tag) {
+					return encodeStructToIndefArray, isEmptyStruct, isZeroFieldStruct
+				}
 				if hasToArrayOption(tag) {
 					return encodeStructToArray, isEmptyStruct, isZeroFieldStruct
 				}
diff --git a/toindefarray_test.go b/toindefarray_test.go
new file mode 100644
index 00000000..98e85aa9
--- /dev/null
+++ b/toindefarray_test.go
@@ -0,0 +1,91 @@
+package cbor
+
+import (
+	"encoding/hex"
+	"testing"
+)
+
+func TestEncodeStructToIndefArray(t *testing.T) {
+	type TestStruct struct {
+		_     struct{} `cbor:",toindefarray"`
+		Data  []byte
+		Count int
+	}
+
+	ts := TestStruct{
+		Data:  []byte{0x73, 0xf7, 0x2d, 0xbe},
+		Count: 3,
+	}
+
+	b, err := Marshal(ts)
+	if err != nil {
+		t.Fatalf("Marshal error: %v", err)
+	}
+
+	h := hex.EncodeToString(b)
+	t.Logf("Encoded: %s", h)
+
+	// Check indefinite array header
+	if b[0] != 0x9f {
+		t.Errorf("Expected first byte 0x9f (indef array), got 0x%02x", b[0])
+	}
+
+	// Check break code at end
+	if b[len(b)-1] != 0xff {
+		t.Errorf("Expected last byte 0xff (break), got 0x%02x", b[len(b)-1])
+	}
+
+	// Decode back
+	var ts2 TestStruct
+	err = Unmarshal(b, &ts2)
+	if err != nil {
+		t.Fatalf("Unmarshal error: %v", err)
+	}
+
+	if hex.EncodeToString(ts2.Data) != hex.EncodeToString(ts.Data) {
+		t.Errorf("Data mismatch: got %x, want %x", ts2.Data, ts.Data)
+	}
+	if ts2.Count != ts.Count {
+		t.Errorf("Count mismatch: got %d, want %d", ts2.Count, ts.Count)
+	}
+}
+
+func TestEncodeStructToIndefArrayNested(t *testing.T) {
+	type Inner struct {
+		_    struct{} `cbor:",toindefarray"`
+		X    []byte
+		Y    int
+	}
+
+	type Outer struct {
+		_     struct{} `cbor:",toindefarray"`
+		Inner Inner
+		Z     int
+	}
+
+	o := Outer{
+		Inner: Inner{X: []byte{0xab, 0xcd}, Y: 42},
+		Z:     7,
+	}
+
+	b, err := Marshal(o)
+	if err != nil {
+		t.Fatalf("Marshal error: %v", err)
+	}
+	t.Logf("Encoded: %s", hex.EncodeToString(b))
+
+	if b[0] != 0x9f {
+		t.Errorf("Expected outer 0x9f, got 0x%02x", b[0])
+	}
+	if b[len(b)-1] != 0xff {
+		t.Errorf("Expected outer 0xff, got 0x%02x", b[len(b)-1])
+	}
+
+	var o2 Outer
+	if err := Unmarshal(b, &o2); err != nil {
+		t.Fatalf("Unmarshal error: %v", err)
+	}
+	if o2.Z != 7 || o2.Inner.Y != 42 {
+		t.Errorf("Decoded mismatch: %+v", o2)
+	}
+}