The paper deals with the analysis of the mechanism of international cooperation in legal proceedings, inparticular cooperation of courts, attorneys, investigators and inquiry agencies with cognizant authoritiesand the officials of foreign states and international organizations, procedure of extraditing persons forcriminal prosecution or enforcing the sentence, the order of transferring a convicted person to the stateof his citizenship. It is noted that international cooperation in criminal justice has been developing forcenturies and shows that this issue has always been complicated for Russia. Until the 20th century, itslow intensity has been determined with many reasons including weak international law, railroads, meansof communication. The situation changed after the establishment of the United Nations Organization, inwhich the USSR played a serious role. However, until USSR collapse, international cooperation in criminalproceedings was sporadic as it was politicized heavily. The related issues were discussed in the onlynormative legal act of a rather general nature. Immediate cooperation of the law-enforcement officials withtheir counterparts was excluded. Hence, Soviet courts, attorneys, investigators were not entitled to filerequests to foreign competent authorities personally regarding criminal cases and get involved in providinglegal assistance. As the new RF criminal code was enforced, the situation changed significantly as thecooperation in criminal proceedings has acquired a developed legal basis having served an impulse todevelop as a pivotal procedural institution. Its legal nature is respecting and following the procedural ordertaking into account national and foreign legislation as to time, space and people involved. The efficiencyof the cooperation in this area depends not only of the possibilities of practical performance of relevantlegal mechanisms but the environment for implementing legal mechanisms.