O'Toole started his career at Shamrock Rovers in 1983. However his first team opportunities were limited and after 16 total appearances in 2 years at Glenmalure Park he signed for Shelbourne in 1985.
He transferred to Leicester City in February 1990. Unable to break into the Leicester first team he was loaned to Exeter City in December 1990, playing six times. In March 1991 he joined Shrewsbury Town where he played 46 league games (almost half as substitute) before being released at the end of the 1992-93 season.
In August 1993 he joined Torquay United, making his debut in midfield as Torquay lost on penalties in the League Cup to Hereford United, with his league debut at right-back in place of Lee Barrow in the 2-1 win away to Darlington on 28 August. He switched to left-back, in place of Scott Colcombe, with Barrow restored at right-back, for the next game, a 1-1 draw at home to Carlisle United and played in the following game, a 3-3 draw at home to Colchester United in which Adrian Foster scored a hat-trick. However, these were his only games for Torquay and he left, joining Bridgnorth Town.
In December 1993 he played 5 league games for Cobh Ramblers and in January 1994 he moved back to his first club. In his two stints at the Hoops O'Toole was unfortunate in that the team were winning the league on those occasions so first team opportunitites were limited.
He joined Halifax Town in April 1994, playing seven times in the Conference before being released at the end of the season.
He spent the 1994-95 and 1995-96 seasons with Stafford Rangers.