This research paper investigates the evolving defense cooperation between India and Japan in the context of the strategic landscape in the Indo-Pacific region, particularly considering China’s rise. The existing literature recognizes China’s increasing influence as a significant factor in India-Japanese security cooperation, but tends to overlook the dynamics behind India’s shifting stance. The study reveals that India initially hesitated to actively engage in anti-China security cooperation with Japan until the mid-2010s, but later adopted a more proactive partnership. An analysis of policy documents, political speeches, and government records attributes India’s initial reluctance to its commitment to non-alignment and strategic autonomy, its desire to balance relations with both China and Japan, and its domestic political priorities favoring economic development over military expansion or strategic alliances. However, growing concerns over China’s assertiveness, military modernization, a change in political leadership, and the Quad’s development as a regional security platform have prompted India’s attitude shift. The research’s recommendations not only offer a roadmap for India, Japan, and other Indo-Pacific countries with deep economic ties to China, but also help combat China’s military threats to contribute to regional stability and security, address common challenges, and foster a peaceful and prosperous Indo-Pacific region.