Brentford were consigned to League Two next season after Crewe ended their survival hopes with victory.
The opening goal came after 18 minutes when Nicky Maynard dummied a Rodney Jack centre and David Vaughan's shot deflected into the back of the net.
And Ryan Lowe drilled in a shot from the edge of the box four minutes later.
Kevin O'Connor pulled a goal back from he penalty spot after Darren Moss handled but Maynard sealed the win with a superb header straight after.
Crewe: Williams, O'Donnell, Moss, Baudet, O'Connor, Rix, Jones, Vaughan (Cox 85), Lowe, Jack (Roberts 82), Maynard (Miller 78).
Subs Not Used: fon Williams, Pope.
Goals: Vaughan 18, Lowe 23, Maynard 70.
Brentford: Nelson, O'Connor, Frampton, Heywood, Brooker, Taylor, Pinault, Keith (Charles 46), Leary (Mousinho 84), Owusu, Kuffour (Willock 57).
Subs Not Used: Abbey, Griffiths.
Goals: O'Connor 69 pen.
Ref: S Bratt (W Midlands).