The effect of fin shape on the mass transfer and pressure loss of a ten-row staggered short pin-fin array in fully developed approaching flow is investigated experimentally using three different fin shapes. The Reynolds number, based on approach-velocity and fin diameter, ranges from 3000 to 18000. The fin shape affects the row-by-row variation of Sherwood number. The results indicate that the stepped-diameter circular fin arrays have not only a larger mass transfer coefficient, but also a smaller pressure loss compared to a uniform-diameter circular fin array. In stepped-diameter circular fin arrays, the effect of step-length-to-total-length ratio on Sherwood number is small, but the total mass transfer rate and pressure loss change significantly with this ratio, owing to differences in mass transfer area and free flow area, respectively.