diff --git a/cmd/wut/cmd_new.go b/cmd/wut/cmd_new.go
index 3ac27c4..5e7aca5 100644
--- a/cmd/wut/cmd_new.go
+++ b/cmd/wut/cmd_new.go
@@ -10,6 +10,7 @@ import (
 	"github.com/simonbs/wut/src/context"
 	"github.com/simonbs/wut/src/git"
 	"github.com/simonbs/wut/src/worktree"
+	"github.com/simonbs/wut/src/worktreeinclude"
 )
 
 func cmdNew(args []string) {
@@ -72,5 +73,7 @@ func cmdNew(args []string) {
 		fail(err.Error())
 	}
 
+	worktreeinclude.Copy(ctx.RepoRoot, worktreePath)
+
 	fmt.Printf("__WUT_CD__:%s\n", worktreePath)
 }
diff --git a/go.mod b/go.mod
index 8b07635..7f227fa 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module github.com/simonbs/wut
 
 go 1.25.6
 
-require github.com/dustinkirkland/golang-petname v0.0.0-20260215035315-f0c533e9ce9b // indirect
+require (
+	github.com/codeglyph/go-dotignore/v2 v2.2.0
+	github.com/dustinkirkland/golang-petname v0.0.0-20260215035315-f0c533e9ce9b
+)
diff --git a/go.sum b/go.sum
index 9f1339f..fa3a6d6 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,4 @@
+github.com/codeglyph/go-dotignore/v2 v2.2.0 h1:9pza2HcxkSzOsihknLZCEAjOeeIPt9uqigbgdLq9qy8=
+github.com/codeglyph/go-dotignore/v2 v2.2.0/go.mod h1:cAH4uxaZ0Rsl33QT2c++wAnk7C8J2c8pik9U4H0+F9w=
 github.com/dustinkirkland/golang-petname v0.0.0-20260215035315-f0c533e9ce9b h1:qZ21OofI7zneC9dOEqul4FmIWz/YjJJMrf6fL7jrFYQ=
 github.com/dustinkirkland/golang-petname v0.0.0-20260215035315-f0c533e9ce9b/go.mod h1:8AuBTZBRSFqEYBPYULd+NN474/zZBLP+6WeT5S9xlAc=
diff --git a/src/worktreeinclude/worktreeinclude.go b/src/worktreeinclude/worktreeinclude.go
new file mode 100644
index 0000000..f16035b
--- /dev/null
+++ b/src/worktreeinclude/worktreeinclude.go
@@ -0,0 +1,189 @@
+// Package worktreeinclude copies untracked files listed in a repo's
+// .worktreeinclude file into a freshly created worktree.
+//
+// Only files that are BOTH matched by a .worktreeinclude pattern AND 
+// gitignored in the source repo are copied, so tracked files are never 
+// duplicated. Errors are swallowed and surface as warnings on 
+// stderr — a misconfigured .worktreeinclude must not break `wut new`.
+package worktreeinclude
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	dotignore "github.com/codeglyph/go-dotignore/v2"
+	"github.com/simonbs/wut/src/git"
+)
+
+// Copy reads <repoRoot>/.worktreeinclude, finds gitignored files matching its
+// patterns, and copies them into worktreePath. Returns the relative paths of
+// the files that were copied. Missing or empty .worktreeinclude is a no-op.
+// Structural errors (read failure, git failure, matcher build failure) cause
+// an early return with no copies; per-file copy failures are logged to stderr
+// and do not abort the rest of the copies.
+func Copy(repoRoot, worktreePath string) []string {
+	data, err := os.ReadFile(filepath.Join(repoRoot, ".worktreeinclude"))
+	if err != nil {
+		return nil
+	}
+
+	patterns := parsePatterns(string(data))
+	if len(patterns) == 0 {
+		return nil
+	}
+
+	matcher, err := dotignore.NewPatternMatcher(patterns)
+	if err != nil {
+		return nil
+	}
+
+	// --directory collapses fully-gitignored dirs (node_modules/, .turbo/, ...)
+	// into single trailing-slash entries. In a large repo this avoids walking
+	// hundreds of thousands of files just to filter them out.
+	out, err := git.Run(
+		[]string{"ls-files", "--others", "--ignored", "--exclude-standard", "--directory"},
+		repoRoot,
+	)
+	if err != nil || strings.TrimSpace(out) == "" {
+		return nil
+	}
+
+	collapsedDirs, files := splitEntries(out, matcher)
+
+	// A .worktreeinclude pattern may target a path inside a collapsed dir
+	// (e.g. `config/secrets/api.key` when all of `config/secrets/` is
+	// gitignored). For those, expand only the dirs the pattern actually
+	// reaches into — expanding every collapsed dir would defeat the perf win.
+	if expand := dirsToExpand(collapsedDirs, patterns, matcher); len(expand) > 0 {
+		args := append(
+			[]string{"ls-files", "--others", "--ignored", "--exclude-standard", "--"},
+			expand...,
+		)
+		expanded, err := git.Run(args, repoRoot)
+		if err == nil {
+			for _, f := range strings.Split(strings.TrimSpace(expanded), "\n") {
+				if f == "" {
+					continue
+				}
+				if ok, _ := matcher.Matches(f); ok {
+					files = append(files, f)
+				}
+			}
+		}
+	}
+
+	copied := make([]string, 0, len(files))
+	for _, rel := range files {
+		src := filepath.Join(repoRoot, rel)
+		dst := filepath.Join(worktreePath, rel)
+		if err := copyFile(src, dst); err != nil {
+			fmt.Fprintf(os.Stderr, "wut: failed to copy %s to worktree: %v\n", rel, err)
+			continue
+		}
+		copied = append(copied, rel)
+	}
+
+	if len(copied) > 0 {
+		fmt.Fprintf(
+			os.Stderr,
+			"wut: copied %d file(s) from .worktreeinclude: %s\n",
+			len(copied),
+			strings.Join(copied, ", "),
+		)
+	}
+	return copied
+}
+
+func parsePatterns(content string) []string {
+	lines := strings.Split(content, "\n")
+	out := make([]string, 0, len(lines))
+	for _, line := range lines {
+		line = strings.TrimRight(line, "\r")
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		out = append(out, line)
+	}
+	return out
+}
+
+func splitEntries(out string, matcher *dotignore.PatternMatcher) (dirs, files []string) {
+	for _, e := range strings.Split(strings.TrimSpace(out), "\n") {
+		if e == "" {
+			continue
+		}
+		if strings.HasSuffix(e, "/") {
+			dirs = append(dirs, e)
+			continue
+		}
+		if ok, _ := matcher.Matches(e); ok {
+			files = append(files, e)
+		}
+	}
+	return dirs, files
+}
+
+// dirsToExpand returns the collapsed dirs that .worktreeinclude actually
+// reaches into. We expand when a pattern's literal prefix lands inside the
+// dir, or when the dir itself matches the include set. We deliberately skip
+// anchorless patterns like `**/foo` or `*.tmp` — for those, expanding every
+// collapsed dir would scan the whole gitignored tree, which is the cost
+// `--directory` exists to avoid.
+func dirsToExpand(dirs, patterns []string, matcher *dotignore.PatternMatcher) []string {
+	out := make([]string, 0, len(dirs))
+	for _, dir := range dirs {
+		if patternsTargetDir(dir, patterns) {
+			out = append(out, dir)
+			continue
+		}
+		if ok, _ := matcher.Matches(strings.TrimSuffix(dir, "/")); ok {
+			out = append(out, dir)
+		}
+	}
+	return out
+}
+
+func patternsTargetDir(dir string, patterns []string) bool {
+	for _, p := range patterns {
+		normalized := strings.TrimPrefix(p, "/")
+		if strings.HasPrefix(normalized, dir) {
+			return true
+		}
+		if globIdx := strings.IndexAny(normalized, "*?["); globIdx > 0 {
+			if strings.HasPrefix(dir, normalized[:globIdx]) {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func copyFile(src, dst string) error {
+	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
+		return err
+	}
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	info, err := in.Stat()
+	if err != nil {
+		return err
+	}
+
+	out, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, info.Mode().Perm())
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(out, in); err != nil {
+		out.Close()
+		return err
+	}
+	return out.Close()
+}