Despite initial optimism, gender mainstreaming often turns into a formalistic exercise whilst losing sight of its broader goal of promoting gender equality. This article suggests that a problem is gender mainstreaming’s largely undefined goal, combined with a rational logic underpinning its implementation. We apply a typology distinguishing substantive, procedural, and combined gender-mainstreaming initiatives to analyze Belgian gender-mainstreaming policies since 1995. Our findings suggest an evolution from more procedural to more combined mainstreaming policies. The rationalist perception underlying gender mainstreaming, in combination with the absence of a gender equality policy objective, turns gender mainstreaming into a formal exercise.