A series of experiments was conducted on two cultivars of sunflower – Helianthus annuus L., viz. FH- 415 and Hysun-33 – to evaluate the effects of various levels and methods of application of two inorganic arsenicals – viz. sodium arsenate (Na₂HAsO₄·7H₂O) – as a source of As⁵⁺ and sodium arsenite (NaAsO₂) as a source of As³⁺ on germination, seedling growth, vegetative growth, and water relation parameters. It was laid out in a completely randomized design with three factors. Notable reductions in GP, SL, and SVI levels with prolonged MGT were recorded under elevated arsenic levels (> 6 mg As/L), whereas the low level of arsenic (2, 4 mg As/L) caused increased SVI. During pot experiment, arsenicals were used in three different ways to evaluate their effects on shoot and root lengths, relative water contents of leaf, succulence, and leaf area at the pre-anthesis stage. Higher levels (80 and 100 mg As/kg) of both salts showed notable stressful impacts as compared to low arsenic concentrations (20 and 40 mg As/kg) in all morpho-physiological parameters recorded. Better shoot and root lengths, water content, number of leaves, and leaf area in the case of FH-415 proved to be a well developed adaptation of this cultivar in an arsenic-contaminated environment.