The Bosnia-Herzegovina international has played a pivotal role in Roma's return to prominence in Serie A this term, missing just two league games as Rudi Garcia's side have looked to keep pace with Juventus.
Though their mission has ultimately proved unsuccessful, the capital club have a return to the UEFA Champions League to prepare for after a two-year absence.
Barcelona, Paris Saint-Germain and Manchester United have been credited with interest in the 24-year-old, whose deal had been set to expire at the end of next season.
But he has committed his future to the Olimpico, ensuring he will be free to take part in the FIFA World Cup with no doubts over his future.
A Roma statement read: "AS Roma wish to announce that an agreement has been reached with Miralem Pjanic for the extension of his current contract, which was was due to expire on June 30, 2015.
"The new agreement is for four years, with an expiration date of June 30, 2018."
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