The accused, Amit alias Tony, had been living in Jaipur under the name of Ashish, said Mandeep Singh Randhawa, DCP (Central).
Based on a tip-off, a police team reached Jaipur on February 22 and contacted locals and labour contractors to gain clues to the accused, he said.
Amit was arrested yesterday, police said.
On March 17, 2015, Amit along with his brother Titu, stabbed Rahul in Karol Bagh and fled the scene.
Rahul succumbed to injuries and a case was registered against Amit based on the evidence from an eye-witness. A reward of Rs 50,000 was declared by Delhi Police on his arrest.
"He did not want to get caught again. Therefore, after murdering Rahul, Amit left for Jaipur and started working as a tailor there. He avoided using mobile phones and did not even contact his family," said Randhawa.