Balanced litters of piglets are crucial for reducing labour demands in piglet care, improving piglet welfare, and increasing survival and uniform growth, which will become even more important with the expected shift in farrowing technologies towards free-farrowing housing systems. This study aims on evaluating the suitability of traits derived from individual piglet birth weight to reduce litter variability in the Czech pig breeding program CzePig. We estimated genomic parameters for piglet birthweight (5,536 litters of Czech Large White and Czech Landrace sows). The analysed traits were mean birth weight (MBW), within-litter standard deviation (SDBW), coefficient of variation of birth weight (CVBW), and the proportion of small piglets in the litter (SMALL). Heritabilities of piglet weight traits were low, with the highest estimates for MBW (0.06 ± 0.019) and SMALL (0.08 ± 0.0210). Heritabilities of litter size traits (number of liveborn and weaned piglets) were 0.05 ± 0.016 and 0.06 ± 0.015. ssGBLUP method showed improved realised accuracy by 4–15% compared with BLUP. MBW had unfavourable nonsignificant correlations with liveborn piglets (−0.39) and favourable with weaned piglets (0.16). Piglet-weight variability traits (SDBW, CVBW, SMALL) were positively or weakly associated with NBA (from 0.06 to 0.30) and negatively with weaned piglets (from -0.23 to -0.32). All genetic correlations were nonsignificant. Incorporating piglet-weight traits, especially the proportion of small piglets, into selection criteria may help litter uniformity a thereby improve piglet survival and welfare, but a slowdown in genetic progress in litter size can be expected.