Updated project metadata. Pathogenic mutations in alpha kinase 3 (ALPK3) cause cardiomyopathy and a range of musculoskeletal defects. How ALPK3 mutations result in disease remains unclear and little is known about this atypical kinase. Using a suite of engineered human pluripotent stem cells (hPSCs) we show that ALPK3 localizes to the sarcomere, specifically at the M-Band. Both sarcomeric organization and calcium kinetics were disrupted in ALPK3 deficient hPSC derived cardiomyocytes. Further, cardiac organoids derived from ALPK3 knockout hPSCs displayed reduced force generation. Phosphoproteomic profiling of wildtype and ALPK3 null hPSC derived cardiomyocytes revealed ALPK3-dependant phospho-peptides were enriched for proteins involved in sarcomere function and protein quality control. We demonstrate that ALPK3 binds to the selective autophagy receptor SQSTM1 (Sequestome 1) and is required for the sarcomeric localization of SQSTM1. We propose that ALPK3 is a myogenic kinase with an integral role in the intracellular signaling networks underlying sarcomere maintenance required for continued cardiac contractility.