$15.3 million for the same period in 2022. The overall increase was driven primarily by increased net interest income of $11.0 million during the nine month period ended September 30, 2023 as compared to the same prior year period.
Interest Income. Interest income increased $7.3 million, or 31.8%, to $30.1 million for the three months ended September 30, 2023 from $22.8 million for the three months ended September 30, 2022. This increase was primarily the result of an increase in the average balance of interest-earning assets, which increased by $62.2 million, or 2.7%, to $2.4 billion for the three months ended September 30, 2023 from $2.3 billion for the three months ended September 30, 2022. Additionally, the average yield of interest-earning assets increased by 111 basis points from 3.95% for the three months ended September 30, 2022 to 5.06% for the three months ended September 30, 2023 as a result of the continued rising interest rate environment.
Interest income increased $27.6 million, or 47.1%, for the nine months ended September 30, 2023 reaching $86.2 million from $58.6 million for the nine months ended September 30, 2022. This increase was driven by a $107.9 million increase in the balance of average interest-earning assets between the two periods. Within the average balance of interest-earning assets, the average balance of loans receivable (net of PPP loans) grew $285.8 million, or 20.7%, between the nine months ended September 30, 2023 and September 30, 2022. In addition, the average yield of interest-earning assets increased by 142 basis points from 3.52% for the nine months ended September 30, 2022 to 4.94% for the nine months ended September 30, 2023 as a result of the continued rising interest rate environment.
Interest income on loans increased by $6.6 million, or 36.3%, to $24.7 million during the three months ended September 30, 2023 from $18.1 million during the three months ended September 30, 2022. The increase in interest income on loans was primarily due to the increase in the average balance of loans (net of PPP loans). The average balance of these loans increased by $199.3 million, or 13.3%, to $1.7 billion for the three months ended September 30, 2023 compared to $1.5 billion for the three months ended September 30, 2022. The average yield on loans, excluding PPP loans, increased by 99 basis points to 5.77% for the three months ended September 30, 2023 from 4.78% for the three months ended September 30, 2022. The increase in the average balance of loans was due to our continued success in growing our commercial real estate, commercial real estate construction, and commercial and industrial loans. The increase in the average yield on loans was the direct result of loans that closed during the first nine months of 2023 that included the impact of the FRB's increase to its benchmark rate during 2022 and the first nine months of 2023.
For the nine months ended September 30, 2023, interest income on loans increased by $23.0 million, or 48.5%, reaching $70.4 million as compared to $47.4 million for the nine months ended September 30, 2022. The increase in interest income on loans represents the continued impact of growth in average loan balances (net of PPP loans) from $1.4 billion for the nine months ended September 30, 2022 to $1.7 billion for the nine months ended September 30, 2023. The increase in average loans outstanding was the result of continued growth within the commercial real estate, commercial real estate construction, and commercial and industrial loan categories. This increase in production was also coupled with an increase in average yield on loans, excluding PPP loans, for the nine month periods from 4.58% in 2022 to 5.64% in 2023. The increase in the average yield on loans was driven by the level of interest rate increases during 2022 and the first nine months of 2023 and the impact on the portfolio during the period.
Interest income on securities increased by $48 thousand, or 1.4%, to $3.5 million during the three months ended September 30, 2023 from $3.4 million during the three months ended September 30, 2022. The increase in interest income on securities was driven primarily by an increase in the average yield on securities during the current period. The average yield on investment securities increased by 36 basis points overall from 2.41% for the three months ended September 30, 2022 to 2.77% for the three months ended September 30, 2023. The increase in the average yield on securities resulted primarily from the deployment of excess cash into higher-yielding securities during 2022. The average balance of securities decreased by $66.9 million, or 11.9%, to $495.8 million for the three months ended September 30, 2023 compared to $562.7 million for the three months ended September 30, 2022. The decrease in the average balance was the combined effect certain maturities had during the quarter as well as a result of the Signature Bank subordinated debt write-off earlier in the year.
For the nine months ended September 30, 2023, interest income on securities increased by $2.3 million, or 28.0%, to $10.6 million during the period from $8.3 million during the nine months ended September 30, 2022. The increase in interest income on securities was primarily the result of an increase in the average yield on securities during the current period. The average yield on investment securities increased by 62 basis points overall from 2.13% for the nine months ended September 30, 2022 to 2.75% for the nine months ended September 30, 2023. The increase in the average yield on securities resulted primarily from the deployment of excess cash into higher-yielding securities as a result of increasing market rates during 2022 and 2023.The average balance of securities decreased by $4.9 million, or 1.0%, to $514.0 million for the nine months ended September 30, 2023 compared to $518.9