The Company’s annualized return on average assets (ROA) and annualized return on average equity (ROE) for the quarter ended March 31, 2021 were 0.82% and 5.92%, respectively, (0.87% and 6.26%, respectively, excluding the merger-related expenses) compared to 0.46% and 3.15%, respectively, for the quarter ended March 31, 2020.
Net Interest Income. Net interest income for the quarter ended March 31, 2021 was $7.2 million, an increase of 5.5%, compared to $6.8 million for the quarter ended March 31, 2020. The increase was primarily the result of a decrease in both the balance and cost of interest-bearing liabilities as well as an increase in the balance of interest-earning assets partially offset by a decrease in the yield on interest-earning assets. The net interest rate spread and net interest margin were 2.71% and 2.96%, respectively, for the three months ended March 31, 2021, compared to 2.70% and 3.02%, respectively, for the three months ended March 31, 2020.
Interest and Dividend Income. Total interest and dividend income decreased $454,000, or 5.0%, to $8.6 million for the three months ended March 31, 2021 compared to $9.0 million for the three months ended March 31, 2020. The decrease was primarily the result of a 47 basis point decrease in the average yield on interest-earning assets to 3.49% for the three months ended March 31, 2021 from 3.96% for the same period in the prior year as a result of lower short-term interest rates. The decrease in total interest and dividend income resulting from the decrease in the average yield was partially offset by an increase in the average balance of interest-earning assets of $78.5 million, or 8.7%, to $985.9 million for the three months ended March 31, 2021 compared to the same period in the prior year.
Interest income on loans decreased $238,000, or 3.1%, to $7.6 million for the three months ended March 31, 2021 compared to $7.8 million for the three months ended March 31, 2020. The decrease was primarily the result of a 23 basis point decrease in the average yield on loans receivable to 4.13% for the three months ended March 31, 2021 from 4.36% for the same period in the prior year. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of loans receivable of $21.6 million, or 3.0%, to $734.0 million for the three months ended March 31, 2021 compared to the same period in the prior year.
Interest income on investment and mortgage-backed securities decreased $104,000, or 10.5%, to $888,000 for the three months ended March 31, 2021 compared to $992,000 for the three months ended March 31, 2020. The decrease was primarily the result of a 59 basis point decrease in the average yield earned on investment and mortgage-backed securities to 1.90% for the quarter ended March 31, 2021 from 2.49% for the same period in the prior year. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of investment and mortgage-backed securities of $27.1 million, or 17.0%, to $186.6 million for the three months ended March 31, 2021 compared to the same period in the prior year.
Dividend income on FHLB and other restricted stock decreased $37,000, or 25.9%, to $106,000 for the three months ended March 31, 2021 compared to $143,000 for the three months ended March 31, 2020. The decrease primarily resulted from a 260 basis point decrease in the average yield to 4.97% for the three months ended March 31, 2021 from 7.57% for the same period in the prior year. The FHLB decreased the dividend yield on both activity and membership stock as of the first quarter of 2021. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of FHLB stock and other restricted stock of $1.1 million, or 15.0%, to $8.7 million for the three months ended March 31, 2021 compared to the same period in the prior year.
Interest income on interest-earning deposits decreased $75,000, or 85.2%, to $13,000 for the three months ended March 31, 2021 compared to $88,000 for the three months ended March 31, 2020. The decrease was primarily the result of a 119 basis point decrease in the average yield on interest-earning deposits to 0.09% for the three months ended March 31, 2021 from 1.28% for the same period in the prior year as a result of lower short-term interest rates. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of interest-earning deposits of $28.7 million, or 103.3%, to $56.5 million for the three months ended March 31, 2021 compared to the same period in the prior year.
Interest Expense. Total interest expense decreased $832,000, or 37.7%, to $1.4 million for the three months ended March 31, 2021 compared to $2.2 million for the three months ended March 31, 2020. The decrease was primarily the result of a 48 basis point decrease in the average cost of interest-bearing liabilities to 0.78% for the three months ended March 31, 2021 from 1.26% for the three months ended March 31, 2020 as a result of lower short-term interest rates. The decrease in total interest expense resulting from the decrease in the average cost was partially offset by an increase in the average balance of interest-bearing liabilities of $15.4 million, or 2.2%, to $716.7 million for the three months ended March 31, 2021 compared to the same period in the prior year.