Apple shares climbed 6.5% after the tech giant's latest results beat expectations, despite seeing a dip in iPhone sales.
The tech-heavy Nasdaq index climbed 29.76 points to 5139.81.
The Dow Jones fell 1.58 points to 18472.17, while the broader S&P 500 slipped 2.6 to 2166.58.
Investors were not expecting the Fed to alter interest rates, but markets were looking for clues as to the timing of any rate moves in the future.
The Fed said household spending was "growing strongly" and the unemployment rate had decreased for the last two months, but inflation was still below its target rate.
Coca-Cola was the big loser on the Dow, falling 3.3%. The company cut its sales forecast for the year and said it was taking steps to address declining demand for its soft drinks.
Twitter shares plunged 14.5% after the company reported a $107m loss on Tuesday.
Aerospace company Boeing saw its share price rise 0.8%. Despite reporting its first loss since 2009, the company beat revenue expectations.
(Close): US stock markets were little moved after the Federal Reserve kept rates unchanged, but strong results from Apple helped lift the Nasdaq.