The permanent ban on gillnets used in shrimp fishing will come in effect from September.
Mexico said it will ban the use of gillnets for shrimp fishing in an area of the northern Gulf of California that is the habitat for the endangered vaquita marina porpoise.
The national fisheries commission said on Wednesday the permanent ban on gillnets used in shrimp fishing will go into effect in September.
The population of vaquita marinas has dropped sharply in recent years to the point that only about 60 survive in the northern Gulf of California, the only place in the world they are found.
The species is believed to be headed for extinction unless conservation measures are adopted.
Scientists attribute the decline to their being caught in the various types of nets used to catch shrimp, sea bass and sharks.
A spokeswoman for the environmentalist group Sea Shepherd said the shrimp net ban was a "good start" but not enough to save the rare porpoise.
"We would hope that they would permanently prohibit all types of gillnets," said Sea Shepherd's Oona Isabelle Layolle.
Nets used to catch sea bass and shark are believed to also be used to illegally fish another endangered species, the totoaba, a type of drum that is much in demand in China.
A temporary ban on the use of those nets has been in place since April 2015 and could be made permanent when it expires in April 2017, Rigoberto Garcia, a fisheries commission official, told AFP.
The Mexican government has pledged to provide $70 million to help fishermen hit by the gillnet ban to make the transition to other methods of fishing.