Luke Wilkshire's wonder strike proved the highlight of Bristol City's win.
Already leading by Steve Brooker's close-range finish on 19 minutes, Wilkshire's volley from 40 yards out caught John Achterberg off his line.
Brooker notched his second on 57 minutes, shooting into an empty net after Achterberg had left his area only to collide with a defender.
Atfter Michael Singer fouled substitute Steven Gillespie, Wilkshire scored with a twice-taken penalty.
Bristol City: Phillips, Coles, Butler, Hill, Bell (Smith 82),
Murray, Doherty (Orr 81), Dinning, Wilkshire, Lita,
Brooker (Gillespie 81).
Subs Not Used: Tinnion, Anyinsah.
Booked: Butler, Doherty.
Goals: Brooker 19, Wilkshire 41, Brooker 57, Wilkshire 90 pen.
Tranmere: Achterberg, Taylor, Jackson, Sharps,
Goodison (Beresford 45), Hall, McAteer (Harrison 45), Rankine,
Roberts, Hume (Haworth 62), Jones.
Subs Not Used: Howarth, Dadi.
Booked: Hume, McAteer, Haworth, Taylor, Jackson.
Ref: T Kettle (Berkshire).