Advocate Yogesh Garg (45) was allegedly shot dead in Mhow on the night of November 18.
The four arrested accused have been identified as real estate dealer Mangilal Thakur, Vikas Chauhan, Sawan Khode and Suresh Singh, Deputy Inspector General of Police (DIG) Santosh Kumar Singh told reporters.
A local lawyers' association and police had announced separate cash rewards on the heads of the alleged killers.
According to initial investigation, the lawyer was creating legal hurdles for Thakur in his land dealings and had also taken huge cash from him, the DIG said.
Further investigation into the case was on, police added.