A riser seal cartridge for an irrigation sprinkler. The cartridge is formed of a rigid self support shell, and a sealing member formed of a resilient material covering the shell in areas which provide the seal. The sealing member includes a first portion which seals the top end of the sprinkler body, a second portion which seals an outer surface of the riser, a third portion which connects the first and second portions, and a fourth portion extending from the third seal portion which provides a seal for the support shell lower end portion. The first seal portion provides a high pressure seal to prevent leakage when the riser is in a fully extended position; and the second seal portion provides a low pressure seal during pressure build-up as the riser is extending.