The passive mode locking of a continuous wave dye laser operating in the blue‐green spectral region is reported for the first time. In a simple linear configuration with no optimization of the intracavity dispersion, coumarin 102, excited by the ultraviolet lines of an argon ion laser, has been mode locked using 3,3’‐diethyl oxacarbocyanine iodide over the spectral range 487–508 nm, yielding pulses as short as 580 fs duration at 498 nm.