BackgroundInterventions for non-communicable diseases are increasingly implemented and evaluated in sub-Saharan Africa, but little is known about their medium- to long-term sustainability beyond the end of research funding. A cluster randomised trial conducted between 2013 and 2016 in Uganda and Tanzania showed that an intervention package to improve hypertension (HT) and type-2 diabetes mellitus (DM) care was highly effective in increasing service readiness and quality of care. The present study assesses the sustainability of the intervention 4 years after the trial in Uganda.MethodsThe study was conducted in 2020 in 22 primary care health facilities (HFs) (3 referrals and 19 lower-level units) that had received the intervention package until trial end (2016), to assess their current capacity and practice to sustain ongoing intervention activities for HT and DM care. Through a cross-sectional survey, 4 pre-defined domains (i.e., cognitive participation, coherence, collective action, and reflexive monitoring) were examined with regard to health worker (HW) normalization and 8 pre-defined domains for intervention sustainability (i.e., organisational capacity, local environment, funding stability, partnerships, communication, evaluation, adaptation, and strategic planning), using the normalisation tool and the program sustainability tool (PSAT). Summary scores were assessed by domains and facility level.ResultsOverall normalization strength was adequate at 4.0 (IQR: 3.8, 4.2) of a possible 5 with no evidence of association with HF level (p = 0.40); cognitive participation (buy-in) and reflexive monitoring (appraisal) were strongest at > 4 across all HF levels. All HF levels were weak (< 4) on collective action (teamwork) and coherence (sense-making). Only collective action differed by level (p < 0.002). Overall intervention sustainability was suboptimal at 3.1 [IQR: 1.9, 4.1] of a possible 7 with weak scores on funding stability (2.0), supportive partnerships (2.2), and strategic planning (2.6). Domain differences by HF level were significant for environmental support (p = 0.02) and capacity in organisation (p = 0.01). Adequate strength at a cut-off mean of ≥5 did not differ by HF level for any domain.ConclusionsFour years after their introduction, practice-dependent intervention elements e.g., local organisational context, HW knowledge or dedication were sustained, but external elements e.g., new funding support or attracting new partners to sustain intervention efforts were not. Whenever new interventions are introduced into an existing health service, their long-term sustainability including the required financial support should be ensured. The quality of services should be upheld by providing routine in-service training with dedicated support supervision.