Tahir took 10 wickets in the ODI series against Sri Lanka which Proteas won 5-0 and completed the double.
"When I started cricket I never thought I'd be No. 1 bowler, it's all the hard work I've done and I'm very excited," ESPNcricinfo quoted Tahir as saying. "There are a lot of good players in world cricket and coming top of that is a really good achievement and I'm really grateful."
"It's an absolute honour playing for South Africa, the boys have helped me over the years and made me the bowler I am today. Credit goes to them as well. I'll try and stay in the spot as long as I can but there are some other brilliant cricketers," he added.
The leggie was twice previously ranked No. 1 in the 50-over format, when he briefly held the top spot during the 2015 World Cup before being leapfrogged by Mitchell Starc at the end of the tournament. Then again in October 2015, and there is a chance of a bowl-off for the position in this series against New Zealand with Trent Boult, the No. 2-ranked bowler.
However, the 37-year-old has not been able to achieve the same success at Test level. In his 20 Test appearances, he has scalped 57 wickets at 40.24.
However, he has performed gracefully in the limited-over format. The leggie has taken 121 wickets at 23.21 in 69 ODIs and 49 at an impressive average of 14.61 in 30 T20Is.
"He doesn't bowl bad balls anymore," his teammate AB de Villiers said last month. "He always used to take wickets but now you don't see bad balls, which makes him really difficult to play," he added.
South Africa will be playing one T20 and a five-match ODI series against the Black Caps. (ANI)