J. Michael Hansen
Executive Vice President and Chief Financial Officer at Cintas
Thanks, Todd, and good morning. Our fiscal 2023 first quarter revenue was $2.17 billion compared to $1.9 billion last year. The organic revenue growth rate adjusted for acquisitions, divestitures and foreign currency exchange rate fluctuations was 13.9%.
Gross margin for the first quarter of fiscal '23 was $1.03 billion compared to $902.8 million last year, an increase of 13.9%. Gross margin as a percent of revenue was 47.5% for the first quarter of fiscal '23 compared to 47.6% last year.
Energy expenses comprised of gasoline, natural gas and electricity were a headwind increasing 30 basis points from last year. Gross margin percentage by business was 47.5% for Uniform Rental and Facility Services, 49.6% for First Aid and Safety Services, 48.8% for Fire Protection Services, and 37.3% for Uniform Direct Sale.
Operating income of $440.1 million compared to $394.1 million last year. Excluding last year's first quarter gain totaling $12.1 million and recorded in selling and administrative expenses, fiscal '23 first quarter operating income increased 15.2% and operating income margin increased 20 basis points to 20.3% from 20.1% last year.
Our effective tax rate for the first quarter was 14.8% compared to 11% last year. The tax rate can move from period to period based on discrete events, including the amount of stock compensation expense.
Net income for the first quarter was $351.7 million compared to $331.2 million last year. Last year's first quarter diluted EPS contained $0.09 from the previously mentioned gain and related income tax expense. Excluding the gain and the related income tax expense, this year's diluted EPS of $3.39 compared to $3.02 last year, an increase of 12.3%.
First quarter operating cash flow increased 13.8%. On June 15, 2022, we paid shareholders $97.7 million in quarterly dividends. Also during the quarter, we purchased $210.8 million of Cintas common stock under our buyback program. We continue to allocate capital in many ways to improve shareholder return. Our strong balance sheet and cash flow enable us to do so consistently.
Todd provided our annual financial guidance. Related to the guidance, please note the following. Fiscal '22 included not only the gain on sale of operating assets in the first quarter, but also a gain on an equity method investment in the third quarter. Excluding these items fiscal '22 operating income was $1.55 billion, a margin of 19.7% and diluted EPS was $11.28. Please see the table in our earnings press release for more information.
Fiscal '23 operating income is expected to be in the range of $1.72 billion to $1.76 billion compared to $1.55 billion in fiscal '22 after excluding the gains. Fiscal '23 interest expense is expected to be approximately $110 million compared to $88.8 million in fiscal '22 due in part to higher interest rates. Our fiscal '23 effective tax rate is expected to be approximately 20%. This compares to a rate of 17.9% in fiscal '22 after excluding the gains and their related tax impacts.
The expected higher effective tax rate will negatively impact fiscal '23 diluted EPS by approximately $0.32 and diluted EPS growth by approximately 290 basis points. Our financial guidance does not include the impact of any future share buybacks and we remain in a dynamic environment that can continue to change. Our guidance contemplates a stable economy and excludes pandemic related setbacks or economic downturns.
I'll turn it back over to Paul.