Silva poured forward in the opening stages with reckless abandon and nearly surprised Fitch with a a choke attempt in the first round.
Fitch regained his composure in the second round and came agonisingly close to ending the fight with a powerful armbar attempt.
Silva tired considerably in the third round and was no match for Fitch in the closing stages as he maintained a relentless pace to earn a unanimous decision on the judges' scorecards.
Fitch told Joe Rogan in the post-fight interview that nothing would have stood in his way from earning a vital win.
He said: "I didn't have a choice, I would have beat anybody today.
"My family needed this win and I needed this win, so I did what I needed to do."
The former UFC welterweight title challenger improves his record to 24-4 in his first fight of 2012.