dividend income in the first quarter of 2021, compared to the first quarter of 2020, was driven by the reduction in market interest rates on loans and securities. Loan growth of $2.4 million was recorded in the year over year period, but interest income on loans declined $1.4 million in the first quarter of 2021, compared to the like period in 2020. Securities available-for-sale increased $143.6 million as of March 31, 2021, compared to March 31, 2020, but interest income recorded on securities available-for-sale decreased $696,000 in the year over year period.
Management has remained diligent in reviewing our loan portfolio to analyze and determine if charge-offs are required. Average loan growth, including loans held for sale, in the first quarter of 2021, compared to the first quarter of 2020, totaled $64.4 million, stemming primarily from 481 PPP loans originated in the first quarters of 2021 totaling $58.3 million, as well organic growth primarily in our commercial, leases, commercial real estate-investor and construction portfolios.
Net Interest Income
Net interest income, which is our primary source of earnings, is the difference between interest income earned on interest-earning assets, such as loans and investment securities, as well as accretion income on purchased loans, and interest incurred on interest-bearing liabilities, such as deposits and borrowings. Net interest income depends upon the relative mix of interest-earning assets and interest-bearing liabilities, the ratio of interest-earning assets to total assets and of interest-bearing liabilities to total funding sources, and movements in market interest rates. Our net interest income can be significantly influenced by a variety of factors, including overall loan demand, economic conditions, credit risk, the amount of nonearning assets including nonperforming loans and OREO, the amounts of and rates at which assets and liabilities reprice, variances in prepayment of loans and securities, early withdrawal of deposits, exercise of call options on borrowings or securities, a general rise or decline in interest rates, changes in the slope of the yield-curve, and balance sheet growth or contraction.
Three months ended March 31, 2021 and 2020
Our net interest and dividend income increased by $885,000 to $23.5 million, for the first quarter of 2021, from $22.7 million for the first quarter of 2020. This increase was attributable to a $2.9 million, or 61.4%, decrease in interest expense for the first quarter of 2021 compared to the first quarter of 2020, partially offset by a $2.1 million decrease in interest and dividend income. The decline in interest expense was due to lower rates for all interest earning deposits in the first quarter of 2021, as well as the redemption of the Old Second Capital Trust I preferred securities and related subordinated debentures in the first quarter of 2020, which increased interest expense by $635,000 due to the acceleration of unamortized debt issuance costs. Net interest and dividend income for the first quarter of 2021 reflected a decrease of $334,000, or 1.4%, compared to the fourth quarter of 2020.
Average earning assets for the first quarter of 2021 were $2.92 billion, reflecting an increase of $116.8 million, or 4.2%, compared to the fourth quarter of 2020, and an increase of $457.5 million, or 18.6%, compared to the first quarter of 2020. Average interest earning deposits with financial institutions totaled $359.6 million for the first quarter of 2021, which reflected an increase of $84.5 million compared to the fourth quarter of 2020, and an increase of $331.6 million compared to the first quarter of 2020. The yield on average interest earning deposits decreased to ten basis points for the first quarter of 2020, from 108 basis points for the first quarter of 2020, which drove the overall reduction in the yield on interest earning assets year over year. Total average loans, including loans held-for-sale, totaled $2.01 billion in the first quarter of 2020, which reflected a decrease of $18.0 million compared to the fourth quarter of 2020, but an increase of $69.4 million compared to the first quarter of 2020. The growth in average loan balances year over year was primarily due to an increase in commercial loans related to PPP loan originations, and organic growth in our leases, commercial real estate-investor, and construction loan portfolios. This growth in loan volumes was offset by the reduction in market interest rates over the past year, which resulted in a decrease in interest income of $1.4 million related to loans in the year over year period. For the first quarter of 2021, the yield on average loans decreased to 4.48%, compared to the yield on average loans of 4.51% for the fourth quarter of 2020, and 4.89% for the first quarter of 2020. Securities also reflected a reduction in interest income year over year, due to decreases in market interest rates over the past year, partially offset by growth in volumes. Total average securities for the first quarter of 2021 increased $50.3 million from the fourth quarter of 2020, and increased $56.5 million from the first quarter of 2020. The yield on average securities declined to 2.49% for the first quarter of 2021, compared to 2.55% for the fourth quarter of 2020 and 3.39% for first quarter of 2020.
Average interest bearing liabilities increased $68.0 million, or 3.9%, in the first quarter of 2021, compared to the fourth quarter of 2020, and increased $161.0 million, or 9.8%, compared to the first quarter of 2020. The growth in average interest bearing deposits of $59.0 million from the prior linked quarter and $162.2 million from the first quarter of 2020 was primarily due to federal stimulus funds received by depositors and growth in depositor liquidity due to market uncertainty related to the COVID-19 pandemic. In addition, we experienced growth in average noninterest bearing deposits of $33.7 million from the prior linked quarter, and $260.3 million from the year over year period, as reductions in market interest rates over the past year have provided less incentive to maintain funds in interest bearing deposits.