Background: An ageing workforce combined with increasing health problems in ageing workers implies the importance of evidence-based interventions to enhance sustainable employability. The aim of this study is to evaluate the effectiveness of the 'Staying healthy at work' problem-solving based intervention compared to business as usual. Methods: This study was designed as a quasi-experimental trial with a one-year follow-up. Measurements were performed at baseline, three and twelve months. The problem-solving based intervention provides a strategy for increasing the awareness of ageing workers of their role and responsibility in living sustainable, healthy working lives. The primary outcomes were work ability, vitality and productivity. Secondary outcomes were perceived fatigue, psychosocial work characteristics, work attitude, self-efficacy and work engagement. Results: Analyses were performed on the 64 workers in the intervention and 61 workers from the business as usual group. No effects on productivity (OR = 0.83, 95% CI 0.23-3.00) and adverse effects on work ability (B = -1.33, 95% CI -2.45 to -0.20) and vitality (OR = 0.10, 95% CI 0.02-0.46) were found. Positive results were found for the work attitude secondary outcome (B = 5.29, 95% CI -9.59 to -0.99), the self-efficacy persistence subscale (B = 1.45, 95% CI 0.43-2.48) and the skill discretion subscale of the Job Content Questionnaire (B = 1.78, 95% CI 0.74-2.83). Conclusion: The results of the problem-solving intervention showed no positive effects on the three outcome measures compared to business as usual. However, effectiveness was shown on three of the secondary outcome measures, i.e. work attitude, self-efficacy and skill discretion. We presume that the lack of positive effects on primary outcomes is due to programme failure and not to theory failure. Trial registration: The trial is registered with the Dutch Trial Register under number NTR2270.