Introduction Healthcare fragmentation, a main cause for delay in cancer diagnosis and treatment, contributes to high mortality in Latin America (LA), particularly among disadvantaged populations. This research focuses on integrated care interventions, which have been limitedly implemented in the region. The objective is to evaluate the contextual effectiveness of scaling-up an integrated care intervention to improve early diagnosis of frequent cancers in healthcare networks of Chile, Colombia and Ecuador. Methods and analysis This research is two pronged: (A) quasi-experimental design (controlled before and after) with an intervention and a control healthcare network in each LA country, using an implementation-effectiveness hybrid approach to assess the intervention process, effectiveness and costs; and (B) case study design to analyse access to diagnosis of most frequent cancers. Focusing on the most vulnerable socioeconomic population, it develops in four phases: (1) analysis of delays and barriers to early diagnosis (baseline); (2) intervention adaptation and implementation (primary care training, fast-track referral pathway and patient information); (3) intracountry evaluation of intervention and (4) cross-country analysis. Baseline and evaluation studies adopt mixed-methods qualitative (semistructured individual interviews) and quantitative (patient questionnaire survey) methods. For the latter, a sample size of 174 patients with cancer diagnosis per healthcare network and year was calculated to detect a proportions difference of 15%, before and after intervention (α=0.05; β=0.2) in a two-sided test. A participatory approach will be used to tailor the intervention to each context, led by a local steering committee (professionals, managers, policy makers, patients and researchers). Ethics and dissemination This study complies with international and national legal stipulations on ethics. It was approved by each country's ethical committee and informed consent will be obtained from participants. Besides the coproduction of knowledge with key stakeholders, it will be disseminated through strategies such as policy briefs, workshops, e-tools and scientific papers.