Hexafluoropropylene oxide-dimer acid (HFPO-DA, trade name GenX), a widespread per- and polyfluoroalkyl substance (PFAS), belongs to a group of synthetic compounds used to manufacture food packaging, plastic, electrical insulators, carbon fiber composites, waterproof fabrics, non-stick coatings, surfactants, lubricants, paints, and fire-fighting foams. GenX is used as a replacement for long-chain PFAS that were phased out due to their bioaccumulative, carcinogenic, and endocrine-disruptive properties, but its potential to be a persistent environmental pollutant is a concern. Hence, evaluating GenX effects on early development is critical to its comprehensive ecological and human-health risk assessment. Zebrafish embryos exposed to GenX concentrations of 0.5 – 20000 mg/L were assessed at 24, 48, and 72 hours post-fertilization. Statistically significant increases were observed in the heart rates of embryos exposed to 2 and 10 mg/L GenX respectively, across all time points. Spinal deformations and edema were evident among embryos exposed to 1000 – 16000 mg/L GenX at 72 hpf. A median lethal concentration, LC50, at 72 hpf of 6514.7 mg/L was established using pH neutralized GenX media, which is significantly greater than the LC50 of 51.12 mg/L calculated using un-neutralized media. Shallow RNA-sequencing analysis of 9465 transcripts identified 38 genes that were consistently differentially expressed at 0.5, 1, 2, and 10 mg/L GenX exposures (compared to control at 72 hpf). Six downregulated genes are associated with neurotransmission and seven with visual response, and seven upregulated genes are expressed in or regulate the cardiovascular system. Our results suggest acute adverse effects by GenX, in early zebrafish development by altering expression of genes involved in or regulating the heart and vascular tissue, neurotransmission, and visual response.