Sickness absence remains a significant issue in Nigerian workplaces, affecting productivity, employee engagement, and overall organisational performance. Building on prior research related to employee wellness and wellbeing in Nigeria, this paper examines how sickness absence affects individual and team performance in key sectors, including healthcare, education, and technology. The study employs the Job Demands-Resources (JD-R) model and the PERMA framework to investigate the relationships among employee health, organisational support, and job outcomes. The findings show that sickness absence has a negative correlation with job satisfaction, productivity, and engagement. However, effective wellness programs can significantly reduce these adverse effects. Recommendations are made for organisations to enhance health management systems, integrate wellness initiatives, and adopt flexible work policies to minimize sickness-related absenteeism and sustain high performance.