One of the most important parts of financial planning is managing one's portfolio so that investment assets can perform at their best with the least amount of risk. Asset allocation, diversification, risk tolerance evaluation, and periodic portfolio rebalancing are some of the important concepts and tactics used in this study. This study explains how the Efficient Market Hypothesis (EMH), Modern Portfolio Theory (MPT), and Capital Asset Pricing Model (CAPM) might help you build a well-rounded investment portfolio. Active and passive investing techniques are compared in the study, which also examines more modern methods of managing portfolios. Passive management aims for long-term growth by monitoring market indexes, but active management requires periodic portfolio modifications to surpass market benchmarks. Key considerations impacting contemporary portfolio management decisions include the function of financial advisers and the influence of technology, especially robo-advisors.