This article examines the Sūraj Prakāś (1843), a devotional historical narrative on the Sikh Gurus by Santokh Singh, to argue that the text mobilizes an Advaitic lexicon within a distinctively Sikh framework of Guru-centred devotion. Drawing on the intellectual training Santokh Singh received at the Giānīā Bungā in Amritsar, the Sūraj Prakāś systemically enumerates Advaita Vedānta concepts only to sublate them into Sikh practices of bhakti and service (sevā). The article situates Santokh Singh within a broader Sikh lineage stretching from Bhai Gurdas (1551–1636) and Mani Singh (1644–1738), while also setting his writings alongside wider early modern devotional Vedānta writers like the Assamese writer, Śaṅkaradeva (1449–1568). Using Michael Allen’s framework of a ‘Greater Advaita Vedānta’ and Rao and McCrea’s notion of an ‘Age of Vedānta’, the article demonstrates how Santokh Singh’s writings exemplify the devotional reworking of non-dual philosophy across sectarian lines. More broadly, it highlights how Sikh scholastic traditions were not passive borrowers of Vedānta but active participants in reshaping it, demonstrating how Advaita was a pliable, transregional idiom that could be domesticated through Guru-centred devotion into what may be called Sikh Advaita.