This paper examines the relationship between Mahayana Buddhism and Hinduism through the lens of Avalokitesvara. To be sure, Avalokitesvara and Isvara represented by Siva or Visnu are most likely two most powerful Isvaras embodied in both traditions. However, Avalokitesvara is a Bodhisattva (enlightened being) and a Mahasattva (great being) in the Mahayana and Isvara is the supreme and ubiquitous deity in Hindu panthelon. In fact, Avalokitesvara represents what an ideal Mahayana savior should be and Isvara is the paramount god for a Hindu devotee. To draw a parallel between them is crucial for us to understand a mutual exchange of thoughts concerning Mahayana and Hinduism. Starting from the name of Avalokitesvara, this investigation then scrutinizes the development of Isvara in Hinduism and Buddhism to explore grave implications of the advent of Alokitesvara in the Mahayana. Through extensive explorations of the related literature, especially Sdharmapunaarika, Karandavyuha, Svetasvatara Upanisad, Narada Purana and Bhagavad Gita, common characteristics shared by Avalokitesvara and Hindu Isvara can be ascertained. Simultaneously, intellectual interaction between Buddhism and Hinduism in medieval India will be accurately pinpointed.