The ratings agency revised down its growth forecasts from 3.2 percent to 2.5 percent for this year, and from 3.8 percent to 3.2 percent for 2015.
Fitch affirmed the country's rating at BBB minus and said its outlook was stable, but warned that the economy remains "highly volatile."
Read MoreTurkey blocks YouTube after Twitter ban
The growth forecasts contrast starkly with the government's own gross domestic product (GDP) target. On Thursday, CBRT Governor Erdem Basci insisted that although the economy was slowing, it was on track to expand at close to 4 percent.
Standard Bank's Ash said it was a "relief" that Fitch did not downgrade the country's rating.
"There is a lot of uncertainty over the outlook for growth, and I guess a wide range of forecasts - last year growth proved very resilient despite forex volatility and political uncertainty/instability," he said in a note.
Social media ban
Turkey has been in the global media spotlight over recent weeks, after moves by the government to ban social media websites in the run up to last weekend's local elections.
In March, access to micro-blogging site Twitter and video sharing site YouTube was blocked, sparking outrage both in Turkey and abroad.
Read MoreTurkey's Twitter ban slammed by politicians, public
A constitutional court in Turkey lifted the Twitter ban on Thursday, but Erdogan said he "did not respect" the ruling, according to Reuters. He argued the court should have rejected the application to allow users back onto the site, the news wire reported.
The blocking of social media sites came amid a corruption scandal in Turkey, which saw angry citizens take to websites like Twitter amid allegations of government wrongdoing, which Erdogan denied.