The rapid proliferation of Internet of Things (IoT) devices has fundamentally transformed the technological landscape, integrating interconnected systems into critical infrastructure, healthcare, industrial automation, and smart homes. However, this expan sive connectivity introduces a myriad of security challenges, as IoT environments often comprise heterogeneous hardware, diverse communication protocols, and complex cloud integrations. This chapter provides a comprehensive exploration of Vulnerability Assess ment and Penetration Testing (VAPT) methodologies specifically tailored for IoT ecosys tems. We systematically examine the distinct attack surfaces of IoT architectures, encom passing hardware interfaces, firmware, network protocols, and associated cloud APIs. A structured proposed methodology is presented, aligning with industry standards such as the OWASP IoT Security Testing Guide, to systematically identify, evaluate, and mitigate vulnerabilities. Furthermore, this chapter presents extensive simulation results and dis cussions derived from an assessment of 50 diverse IoT devices, analyzing the distribution of vulnerabilities, risk severity, and remediation timelines. The findings underscore the critical necessity of multi-layered security assessments to fortify IoT environments against evolving cyber threats and ensure compliance with emerging regulatory frameworks.