diff --git a/cli/cli.go b/cli/cli.go
index 9ddec900..524b737e 100644
--- a/cli/cli.go
+++ b/cli/cli.go
@@ -13,10 +13,11 @@ type Format struct {
 	WorkingDirectory      kong.ChangeDirFlag `default:"." short:"C" help:"Run as if treefmt was started in the specified working directory instead of the current working directory."`
 	NoCache               bool               `help:"Ignore the evaluation cache entirely. Useful for CI."`
 	ClearCache            bool               `short:"c" help:"Reset the evaluation cache. Use in case the cache is not precise enough."`
-	ConfigFile            string             `type:"existingfile" default:"./treefmt.toml" help:"The config file to use."`
+	ConfigFile            string             `type:"path" help:"Load the config file from the given path (defaults to finding treefmt.toml up)."`
 	FailOnChange          bool               `help:"Exit with error if any changes were made. Useful for CI."`
 	Formatters            []string           `short:"f" help:"Specify formatters to apply. Defaults to all formatters."`
-	TreeRoot              string             `type:"existingdir" default:"." help:"The root directory from which treefmt will start walking the filesystem."`
+	TreeRoot              string             `type:"path" help:"The root directory from which treefmt will start walking the filesystem (defaults to the directory containing the config file)."`
+	TreeRootFile          string             `type:"path" help:"File to search for to find the project root (if --tree-root is not passed)."`
 	Walk                  walk.Type          `enum:"auto,git,filesystem" default:"auto" help:"The method used to traverse the files within --tree-root. Currently supports 'auto', 'git' or 'filesystem'."`
 	Verbosity             int                `name:"verbose" short:"v" type:"counter" default:"0" env:"LOG_LEVEL" help:"Set the verbosity of logs e.g. -vv."`
 	Version               bool               `name:"version" short:"V" help:"Print version."`
diff --git a/cli/format.go b/cli/format.go
index a9fe7640..e41fbe50 100644
--- a/cli/format.go
+++ b/cli/format.go
@@ -69,6 +69,40 @@ func (f *Format) Run() (err error) {
 		}
 	}()
 
+	// find the config file unless specified
+	if Cli.ConfigFile == "" {
+		pwd, err := os.Getwd()
+		if err != nil {
+			return err
+		}
+		Cli.ConfigFile, _, err = findUp(pwd, "treefmt.toml")
+		if err != nil {
+			return err
+		}
+	}
+
+	// search for the project root unless specified
+	if Cli.TreeRoot == "" {
+		// use the location of the treefmt.toml file by default
+		dir := filepath.Dir(Cli.ConfigFile)
+
+		// search using the --tree-root-file if specified
+		if Cli.TreeRootFile != "" {
+			pwd, err := os.Getwd()
+			if err != nil {
+				return err
+			}
+			_, dir, err = findUp(pwd, Cli.TreeRootFile)
+			if err != nil {
+				return err
+			}
+		}
+
+		Cli.TreeRoot = dir
+	}
+
+	log.Debugf("config-file=%s tree-root=%s", Cli.ConfigFile, Cli.TreeRoot)
+
 	// read config
 	cfg, err := config.ReadFile(Cli.ConfigFile, Cli.Formatters)
 	if err != nil {
@@ -384,3 +418,56 @@ func applyFormatters(ctx context.Context) func() error {
 		return nil
 	}
 }
+
+func findUp(searchDir string, fileName string) (path string, dir string, err error) {
+	for _, dir := range eachDir(searchDir) {
+		path := filepath.Join(dir, fileName)
+		if fileExists(path) {
+			return path, dir, nil
+		}
+	}
+	return "", "", fmt.Errorf("could not find %s in %s", fileName, searchDir)
+}
+
+func eachDir(path string) (paths []string) {
+	path, err := filepath.Abs(path)
+	if err != nil {
+		return
+	}
+
+	paths = []string{path}
+
+	if path == "/" {
+		return
+	}
+
+	for i := len(path) - 1; i >= 0; i-- {
+		if path[i] == os.PathSeparator {
+			path = path[:i]
+			if path == "" {
+				path = "/"
+			}
+			paths = append(paths, path)
+		}
+	}
+
+	return
+}
+
+func fileExists(path string) bool {
+	// Some broken filesystems like SSHFS return file information on stat() but
+	// then cannot open the file. So we use os.Open.
+	f, err := os.Open(path)
+	if err != nil {
+		return false
+	}
+	defer f.Close()
+
+	// Next, check that the file is a regular file.
+	fi, err := f.Stat()
+	if err != nil {
+		return false
+	}
+
+	return fi.Mode().IsRegular()
+}