This chapter provides an overview of the mental status examination (MSE), a structured clinical assessment and evaluation of a client’s behavioral, emotional, and cognitive functioning. The chapter details key components of the MSE beginning with general client observations such as arrival, appearance, and behavior, all while emphasizing the importance of keen observation and cultural sensitivity in interpreting these cues. It then delves into specific domains of the MSE, including thinking, emotion, and cognition, detailing how thought process and content, mood, affect, perceptual disturbances, and functional ability are assessed. The chapter illustrates diverse manifestations of psychological functioning and client behaviors through detailed descriptions and case examples. Special attention is given to nuances in speech, behavior, and emotional expression, with an emphasis on differentiating between typical variations and indicators of psychopathology. The chapter underscores the importance of considering contextual factors related to different settings and populations, including telehealth and cultural considerations, and evaluating client strengths throughout the process. This approach ultimately emphasizes the collaborative and holistic nature of clinical assessment. Overall, this chapter serves as a comprehensive guide for clinicians to effectively use the MSE to gain insights into a client’s psychological well-being, inform therapeutic interventions, and communicate with other professionals.