Objective: This study aimed to determine the evolution of Instagram use, body dissatisfaction and physical appearance comparisons throughout the coronavirus disease-2019 (COVID-19) pandemic, and to explore whether there was a relationship between the changes in Instagram use throughout the pandemic and body dissatisfaction and physical appearance comparisons. Method: A total of 272 Spanish women (16–70 years old) were followed-up across four waves of assessment between November 2019 (before the pandemic started) and July 2021. Body dissatisfaction, social appearance comparisons, and Instagram use were assessed using the Eating Disorders Inventory-3, the Physical Appearance Comparison Scale-Revised, and an ad hoc questionnaire for Instagram use, respectively. Results: No statistically significant changes were found in the frequency of Instagram use, nor on the proportion of women following appearance-focused accounts on Instagram, among the data collection periods. Body dissatisfaction significantly increased from T1 to T4, and physical appearance comparisons significantly increased from T1 to T2, T3, and T4. These increases were not found to be significant for those with eating disorder risk. No significant differences were found in body dissatisfaction and physical appearance comparisons depending on whether participants' frequency of Instagram use had changed or remained the same, or whether they had started/stopped/continued following appearance-focused accounts on Instagram during the pandemic. Discussion: Women's body dissatisfaction and physical appearance comparisons seem to have increased throughout the pandemic. The experiences of individuals with eating disorder risk throughout the pandemic, and the relationship between the pandemic and Instagram use, might be complex and need further research. Public Significance: This study suggests that women's body dissatisfaction and physical appearance comparisons have increased throughout the COVID-19 pandemic. However, this increase might not be as clear for those who had eating disorder risk before the pandemic. Instagram frequency of use, and the percentage of women following appearance-focused accounts on Instagram, do not seem to have significantly increased. More research is needed to explore the impact of the pandemic.