The authors describe a national corporate team–based weight loss intervention targeting groups of overweight/obese employees and assess its effectiveness. A 12-week weight loss program comprising nutrition education and physical activity sessions, enhanced by a nationwide media campaign, was organized by the Singapore Health Promotion Board. A total of 285 participants, forming 72 teams (1 per workplace), had their anthropometric (weight, body mass index [BMI], and body fat percentage) and fitness (fitness index score based on UKK 2-km walk test) measurements taken pre-intervention and post-intervention. Average decreases, from baseline to end of intervention, in weight, BMI, and body fat percentage were 3.58 kg, 1.32 kg/m², and 2.14%, respectively. The fitness index score increased by 34.1 units. Greater participation in physical activity and nutrition education sessions was associated with more beneficial anthropometric and fitness changes. The intervention was well received and effective in producing short-term weight loss. Further research needs to be done to ascertain its long-term effectiveness and generalizability.