Systematic Investment Plans (SIPs) have become one of the most preferred options for investing in mutual funds, due to their cost-effectiveness, disciplined investment strategy, benefit of rupee cost averaging, and potential for long-term wealth accumulation. The current study reviews the existing literature published between 2016 and 2026 on SIP adoption and investment behaviours in mutual funds. A total of 20 research articles were chosen from different academic journals, conference proceedings, and thesis. The studies that were reviewed were assessed based on their objectives, sample sizes, examined variables, research methodologies, statistical methods, and significant findings. The review indicates that factors such as investor awareness, financial literacy, professional management, risk perception, anticipated returns, convenience, and social influences are key determinants in the adoption of SIPs. Investment decisions are also significantly influenced by behavioral characteristics like present bias, herding behavior, and loss aversion. The study also identifies important obstacles such as lack of trust, financial limitations, market risk concerns, and ignorance. The review identifies several research gaps, especially with relation to social media influence, digital investing platforms, behavioral biases. The results give a thorough insight of SIP investment behavior and suggest future lines of inquiry for mutual fund investment decision-making.