Members of trade unions 1, 2 and 3 had voted in favour of strike action last month, saying the state-owned miner's final offer had made "a mockery" of their demands.
Workers and their supporters marched "for dignity" in Calama on the weekend.
The company is planning to cut more than 1,000 jobs as it transitions the 104-year-old mine to an underground operation as part of a plus-US$5 billion investment to extend the minelife.
The unions, that represent 3,200 workers, have said they wanted improvement in health care, equality between workers and retirement benefits.
"We open Chuqui with a strike and we will close fighting for our dignity and the equality of those who work for Chile's salary," Sindicato 3 president Rolando Milla said on Twitter yesterday.
Codelco has reportedly said it regretted the unions' decision and said its offer had been "serious, responsible and realistic", particularly given the uncertainties surrounding US-China trade tensions.
"The strike at Codelco's Chuquicamata copper mine has begun," Marex Spectron's Dee Perera on the London Metal Exchange desk noted on Friday, adding that Shanghai Futures Exchange coppery inventory had extended declines.
Copper closed slightly lower on the LME on Friday at $5,822/t.
