Following the incident, Pakistan has played the majority of its "home" series in the United Arab Emirates (UAE), while Lahore has been the only destination for a select number of worldwide and PSL games played in Pakistan.
"I have been working day and night to conclude an agreement with West Indies which I have just finalised an hour ago", Sethi said.
"Good news! West Indies have agreed to play three T20 matches in Karachi on 1st, 2nd and 4th April", wrote the PCB chief on Twitter, adding: "CM Sindh is fully supporting this PCB initiative".
Earlier, Lahore was selected as the venue of the West Indies matches but later Karachi was declared safe by worldwide security experts which is why all the three T20Is will be played in Karachi.
Lahore's Gaddafi Stadium hosted two Twenty20 and three one-day internationals against Zimbabwe in 2015; last year's final of the PSL and three T20 internationals against a World XI; as well as a T20 global match against Sri Lanka, demonstrating the country's improved security.
Sethi said Reg Dickason, the ICC's security consultant, would visit Karachi during the PSL final to look at the security arrangements for the series.
In view of the increasing demand of tickets for the PSL final, the cricket board has turned two general enclosures of National Stadium into VIP Enclosures.
Pakistan and West Indies will play T20Is on three consecutive days after Pakistan Cricket Board has rescheduled the series itinerary on the request of Sindh Government.
Sethi had last year announced a five-year plan that involved the West Indies touring Pakistan every year until 2022, but in January walked back on that claim due to the costs involved.