Introduction Dypsis decaryi seeds need more phytochemical and biological attention specially on one of the most important life-threatening problems (cancer). Methods Total ethanol extract of D. decaryi seeds (TEEDDS, Arecaceae) and its fixed oil fraction (FOF) were subjected to UPLC-HR-ESI-MS metabolic profiling and gas chromatography-mass spectrometry, respectively. Also, TEEDDS, FOF, and FOF silver nanoparticles (FOF-SNPs) were screened using 4 cell lines. FOF effects on expression of Bcl-2, Bax, P53, and epidermal growth factor receptor (EGFR) in human prostate carcinoma cell line (PC-3) were evaluated and supported by docking study. Results Metabolic profiling of TEEDDS resulted in identification of 18 compounds. While GC-MS of FOF displayed the presence of 12 fatty acids methyl esters. TEEDDS, staurosporine, FOF, and FOF-SNPs showed IC50= 3.55, 9.81, 16.88, and 0.01 µg/mL, respectively, against PC-3 (human prostate carcinoma cell line). FOF effects on the expression of Bcl-2, Bax, P53, and EGFR in PC-3 cell lines displayed IC50= 1.09, 220.6, 619.8, and 399.64 ng/mL, respectively. The FOF major constituent (E-13-octadecenoic acid) exhibited significant affinity and binding interactions that were comparable with that of the cocrystalized inhibitor.