AimsThe pandemic resulted in a lifestyle crisis which may negatively affect patients with diabetes. Despite current knowledge, there is a lack of longitudinal studies evaluating this effect. To assess patients' perceptions about changes in lifestyle, and eating and sleeping patterns after 18 months of the COVID-19 pandemic, and to identify if aspects related to the pandemic (social distancing, COVID-19 infection, behavioral changes, and financial difficulties) are predictors of worsening in eating and sleeping parameters. Methods This was a longitudinal study that followed patients with diabetes from April 2020 to July 2021 in Southern Brazil. Individuals with type 1 or type 2 diabetes, aged ≥ 18 years, were included. The outcome of this study was the assessment of daily habits during a 18-month period of the COVID-19 pandemic. Specific questionnaires were applied once participants were included in this study (3 months after the onset of the pandemic) and at the 18-month follow-up, which included the Eating Attitudes Test-26 (EAT-26), the Mini-Sleep Questionnaire (MSQ), and a specific questionnaire on diet, physical activity, and sleep pattern. Data were compared within and between groups (type 1 and type 2 diabetes), and multivariable models were used to identify subgroups of worse outcomes. Results A total of 118 (78.6%) participants remained in the study at follow-up (mean age 54.6 ± 13.9 years, 41.3% male). In total, 33.9% of participants perceived weight gain during the pandemic, especially those with type 1 diabetes (43.1% vs 25.0% in type 2 diabetes, P = 0.04). About one in four participants reported emotional eating and changes in their eating habits for financial reasons. Regarding sleep patterns, more than half the participants reported taking naps during the day, out of which 30.5% of them perceived worse sleep quality, with no difference between type 1 and type 2 diabetes groups. There were no within-group differences in MSQ and EAT-26 scores. Among participants with type 2 diabetes, age ≥ 60 years (OR 27.6, 95%CI 2.2-345.7), diabetes duration ≥ 15 years (OR 28.9, 95%CI 1.4-597.9), and perceived emotional eating (OR 10.9, 95%CI 1.1-107.5) were associated with worsened food quality. Worse sleep quality during the pandemic was associated with age ≥ 60 years for both type 2 diabetes (OR 5.6, 95%CI 1.1-31.5) and type 1 diabetes (OR 5.5, 95%CI 1.0-29.9). Conclusions Follow-up data from a cohort of patients with diabetes indicate that at the end of 18 months of social distancing, some lifestyle aspects worsened and some improved, showing that these patients responded differently to the adversities of this period. The evidence of clinical features associated with worsening in food and sleep quality provides new insights to prioritizing actions in crisis situations.