This design case describes three iterative development phases of online integration training design from 2015 to 2021. Online integration training is a public educational service for adult immigrants who are registered as unemployed in Finland. The learners are from diverse backgrounds, typically residing in sparsely populated areas or unable to attend classroom education for other reasons. Fully online and starting from language proficiency level zero, this full-time integration training design is among the first of its kind globally. Many participants had no prior experience studying online, and their digital skills varied widely. Initial impact expectations were low. This case illustrates how an accessible and collaborative online training design promotes inclusivity and agency in a new homeland. Development challenges between design iterations, particularly involving interaction among stakeholders, teacher workload, and learner engagement. The best design for learners wasn’t necessarily the best for teachers, prompting compromises in design to ensure optimal functionality for all users. Results exceeded expectations in language and cultural learning outcomes and subsequent placements. Quality stemmed from the design’s interactivity, attractiveness, practicality, shareability, and repeatability. The unique features of immigrants’ online learning and the significant increase in immigration require further effective educational solutions in the future. Harnessing new technologies to respond to international workforce mobility and precisely coded co-design will enhance the effectiveness of online education services.