Damien O’Rourke had earlier headed Mervue into the lead straight from Alan Murphy’s 64th-minute corner, but substitute Lyons sealed a deserved point for the hosts.
After Pat Hoban’s header crashed off the post eight minutes in for Mervue, SD Galway took the lead five minutes later when former Mervue striker Enda Curran tucked past Brian O’Donoghue.
SD Galway continued to dominate with Curran and Mike Tierney both coming close to doubling their advantage. But right on the cusp of half-time Gary Kelly pulled Mervue level with a blistering shot into the corner of Ronan Burke’s net to send the side in 1-1 at the break as the sides shared the spoils.
SD GALWAY: Burke; Harty, Quinlan (Browne, 27), Geraghty, Bradshaw; McConnell, Greaney, Conlon, Tierney (Dusi, 88), Gaffney; Curran (Lyons, 71).
MERVUE UNITED: O’Donoghue; Farrell, McEntee, O’Rourke, Ludden; Kelly, Lee, Murphy (Keegan, 86), Varley; Hoban, Molloy (Nkololo, 82).
Referee: Ray Matthews