Fruit quality is most important for commercially cultivated watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] cultivars and introgression of resistance gene from wild or related species is a major challenge and imperative to study the inheritance of internal and external fruit quality traits for utilizing in resistance breeding programme. Present study was carried out at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi during summer 2020 to 2022 involving 4 seasons for identifying source of resistance, developing F1 and other subsequent generations (F2, BC1P1 and BC1P2) and evaluation of parental lines along with breeding population in watermelon. The resistant line DWM-45 was used as a female parent and crossed with commercially popular sweet watermelon variety Arka Manik to produce F1 and other generation to study the inheritance of internal and external fruit quality traits. Based on the segregation pattern of progeny it is concluded that fruit shape, rind pattern, seed coat colour and colour of flesh at margin near rind and at carpellar region followed monogenic inheritance. Furthermore, our findings revealed a complex genetic control with epistatic interactions for other fruit quality traits such as fruit length, fruit width, fruit weight and total soluble solids. This study provides valuable insights into the genetic basis of various fruit quality traits in watermelon which can have practical applications in breeding programmes, facilitating the development of improved watermelon varieties with desirable fruit characteristics.