Expansion of cross-sectional area of flow passages in micro-pin-fin heat sinks provides advantages due to suppression of bubble-confinement problem. However, low mass flux in addition to orientation of fins and existence of artificial nucleation sites have great potential in terms of influencing performance of expanding heat sinks. Therefore, in this study, different types of expanding micro-pin-fin heat sinks at a low mass flux (G = 98 kg m−2 s−1) are experimentally investigated for saturated conditions. At a low fluid content, effectiveness of inline or staggered fin configuration and artificial nucleation sites are evaluated via three different expanding heat sinks. For the whole database, B-Type (expanding, having artificial nucleation sites, inline fins) increases the heat transfer coefficient up to 25.5% against A-Type (expanding, no artificial nucleation sites, inline fins). C-Type heat sink (expanding, having largest cross-sectional area at the downstream region, no artificial nucleation sites, staggered fins) is exposed to serious instabilities, early reaches critical heat flux (CHF). Due to CHF, first five data can be obtained for C-Type; therefore, up to 130 W, on first five data, A-Type increases heat transfer coefficient up to 1011% compared to C-Type; while B-Type increases heat transfer coefficient up to 1101.3% compared to C-Type.