In India, marigold (Tagetes spp.) stands out as a prominent flower crop, widely cultivated for various purposes such as loose flowers, cut flowers and pot plants. However, the inconsistent seed development in the central portion of the capitulum can lead to poor seed quality. To address this issue, a study was conducted on three marigold varieties (Pusa Deep, Dainty Marietta, and Pusa Bahar) during both rainy and winter seasons in Delhi. The research aimed to understand the impact of sink modification within the capitulum on seed quality parameters. Three distinct treatments were implemented for sink modification: removing outer and middle whorls (T1), maintaining a single flower per branch (T2), and a combination of maintaining a single flower per branch while removing outer and middle whorls (T3). The study extensively examined seed quality parameters, encompassing seed germination, seedling length, seedling dry weight, vigour indices, seed characters, and biochemical traits. Results revealed that sink modification, specifically in T3, significantly enhanced seed quality. T3 exhibited superior characteristics, including higher germination (48.3%), increased seedling length (9.6cm), greater seedling dry weight (12.0mg), and higher vigour index-II (582.8). Remarkably, T3 recorded maximum values for the 1000-seed weight (1.5g), area size (11.5mm2), seed length (12.8mm) and perimeter length (28.1mm). Also, T3 had higher total soluble content (23.63mg/gm FW) and sucrose synthase activity (1684.81μg/min/gm FW). This study underscores the significance of sink modification in enhancing marigold seed quality, revealing that competition for food reserves significantly influences variations in seed quality among different floret positions.