this.heroForm = new FormGroup({ 'name': new FormControl(this.hero.name, [ Validators.required, Validators.minLength(4), forbiddenNameValidator(/bob/i) // <-- Here's how you pass in the custom validator. ]), 'alterEgo': new FormControl(this.hero.alterEgo), 'power': new FormControl(this.hero.power, Validators.required) });