Purpose: Studies investigating the influence of comorbidities on patient-reported outcomes after acute Achilles tendon ruptures (ATR) are lacking. In this study, the aim was to investigate the effect of comorbidity and medical treatment on the patient-reported outcome measure Achilles tendon total rupture score (ATRS). Methods: The study was performed as a registry study from the Danish Achilles tendon Database (DADB). In the DADB, ATRS was registered at baseline (prior to rupture), at 3–6 month, 1-year and 2-year follow-ups. The outcomes were ATRS at follow-up and the change in ATRS from baseline to follow-up. Variables of interest were diabetes, hypertension, rheumatic disease and treatment with orally administrated corticosteroids. Linear mixed-effects models including all follow-up time points in the same model were used adjusting for sex, age group, treatment (operative or non-operative) and the investigated comorbidities. Results: Data were collected from 2012 to 2019. Two thousand and four patients with ATR were included. Patients with the investigated comorbidities and treatment with orally administrated corticosteroid scored 10.6–19.1 points lower in mean ATRS at baseline (prior to rupture) compared to patients without the respective disease or treatment. At follow-up, patients with diabetes (mean difference, [95% CI]) (− 6.2, [− 11.7; − 0.8]; P = 0.03) and patients in treatment with orally administrated corticosteroids (− 10.9, [− 16.2; − 5.7]; P < 0.01) had a statistically significantly worse ATRS than patients without the respective disease. However, change in ATRS from baseline to follow-up was not affected. Hypertension and rheumatic disease did not affect ATRS at follow-up but had a positive effect on change in ATRS (4.3, [0.5; 8.1]; P = 0.03) and (12.0, [5.0; 19.9]; P < 0.01), respectively. No other statistically significant differences were found. Conclusion: This study showed that patients with diabetes, hypertension, rheumatic disease and patients in treatment with orally administrated corticosteroids had a lower ATRS at baseline (prior to the rupture) when compared to patients without the respective disease or treatment. Diabetes and treatment with orally administrated corticosteroids did negatively affect ATRS at follow-up, but none of the investigated comorbidities or treatment with orally administrated corticosteroids did negatively affect change in ATRS from baseline to follow-up. Level of evidence: Level III.