A stand-on riding mower has a support platform at the rear thereof for supporting an operator who stands during operation of the mower. The support platform is pivotally connected to the traction frame of the mower by a suspension that includes pivotal support plates at each side of the platform. At least one spring is arranged to push against the pivotal support plates in a direction causing the platform to rise such that the weight of the operator atop the platform causes the platform to lower until increasing biasing force in the spring balances the operator's weight. The spring ensures that impact shocks and the like on the traction frame of the mower are cushioned before reaching the operator's platform. In addition, the operator's platform is pivotal relative to the support plates to allow the operator's platform to be disposed in both a vertical stowed position and a horizontal deployed position.