This article exploits a change in the vesting rules for employer‐sponsored pension plans introduced by the Tax Reform Act of 1986 to identify the causal effect of pension portability legislation on workers' voluntary mobility decisions. We pool data from different years of the Survey of Income and Program Participation to estimate the impact of this reform using difference‐in‐differences methods. Our results suggest that the reform had a positive and significant impact on voluntary job mobility of the treatment group. (JEL J24, J44, J62, J63, J68)