Introduction: This study evaluated the feasibility of a large longitudinal cohort study utilizing an online platform to investigate the association and predictive relationship of working alliance, outcome expectations, adherence and self-efficacy with outcome in Achilles tendinopathy. The objectives were: (1) to determine the recruitment and retention rate and (2) to carry out preliminary data analysis of the selected variables and clinical outcomes. Methods: A multi-centred, longitudinal feasibility cohort study was used. Eligible participants were directed to a bespoke online platform hosting study information and the outcome measures in the form of an online questionnaire. Responses from the online questionnaire were collected on three occasions: at baseline, at 6 and at 12 weeks following completion of the first questionnaire. Feasibility outcomes (recruitment and retention rates) were described using descriptive statistics. Results: The website recorded a total 55 views. These 55 views resulted in 24 participants consenting to join the study. The questionnaire at baseline was started 63 times and completed on 60 separate occasions resulting in a 95% conversion rate. Retainment for completion of the questionnaire for a second time was 83.3% and for the third time was 66.6%. All questionnaires were completed fully yielding a missing data indicator of 0%. Conclusions: Feasibility studies ask the question ‘can this be done’? Based on the data from recruitment and rates and exploratory correlation analysis a future study can be done; this previously untested online platform appears feasible, but changes could be useful before proceeding to a much larger study.