Aim To study potential socioeconomic differences within the general decline in breastfeeding over time. Methods Data was collected for 51 415 infants born 2004–2010 from the databases of statistics of the Preventive Child Health Care Services in Uppsala and Orebro counties in Sweden and socioeconomic indicators from Swedish national registers. Breastfeeding data (breastfed/not breastfed) from 1 week, 4 months and 6 months of age were used as the main outcome variables. Educational level of the mother was defined as the highest level on a three‐grade scale, low, medium and high. Family type was defined as whether the mother was single or married/cohabiting. Family disposable income was divided into quartiles where quartile 1 included the 25% children in families with the lowest incomes. Analyses were conducted by logistic regression models using the methodology of generalized estimating equations (GEE). An exchangeable correlation structure was used to control for the dependence among infants with the same mother. Results Breastfeeding rate in Sweden has declined gradually since the late 1990s. The results indicated that overall breastfeeding rates over the study period were influenced by socioeconomic status in a gradient manner but no widening socioeconomic gap was detected. Rather the interaction analyses showed a narrowing socioeconomic gap over the study period between high and low educational level and single versus cohabiting mothers at 4 months. The narrowing socioeconomic gap between the educational level categories was also detectable at 6 months. Conclusion No increase in socioeconomic gap was detected within the general decline in Swedish breastfeeding. However, there are reasons to maintain and strengthen the overall breastfeeding supportive measures including extended support for vulnerable groups.