The West Indies paceman finished off Leicestershire's innings with three wickets in the 39th over to finish with career-best Sunday figures of five for 23.
Leicestershire could manage only 206 all out and Gloucestershire reached their target with two balls to spare, Mark Alleyne top scorer with 63.
Meanwhile, Walsh's West Indian team-mate Brian Lara could only watch from the pavilion, suffering a bruised leg, as his Warwickshire team romped to a 47-run win over struggling Derbyshire. Lara was injured when he pulled a ball from Dominic Cork into his leg in the 15th over of Warwickshire innings and collapsed in obvious distress.
After a lengthy delay, Lara batted on with Nick Knight as his runner and the England opener later took over the captaincy when Warwickshire fielded.
Shaun Udal returned career-best Sunday figures of five for 43 to guide Hampshire to an easy win over Surrey. Udal went through the middle order to enable Hampshire to clinch their third win in four matches by 75 runs.Reuse content