Rhabdomyosarcoma (RMS) is an aggressive and difficult to treat cancer characterized by a muscle-like phenotype. Although the average 5-y survival rate is 65% for newly diagnosed RMS, the treatment options for metastatic disease are limited in efficacy, with the 5-y survival rate plummeting to 30%. Heterogenous nuclear ribonucleoprotein H1 (HNRNPH1) is an RNA-binding protein that is highly expressed in many cancers, including RMS. To determine the role HNRNPH1 plays in RMS tumorigenesis, we investigated its expression and effect on growth in three cellular models of RMS: RD, RH30, and RH41 cells. Upon knockdown of HNRNPH1, growth of all cell lines was reduced, most likely through a combination of apoptosis and cell cycle arrest. We then recapitulated this finding by performing in vivo xenograft studies, in which knockdown of HNRNPH1 resulted in a reduction of tumor formation and growth. We used RNA sequencing to identify changes in gene expression after HNRNPH1 knockdown and found altered splicing of some oncogenes. Our data contribute to understanding the role of HNRNPH1 in RMS development.