The 33-year-old, currently playing in the second Test against New Zealand in Dubai, will be available for the entire County Championship and Royal London One-Day Cup campaigns in his second spell at Taunton.
Azhar will not play for Pakistan at next year's World Cup in England and Wales, having retired from One-Day Internationals, making him available for the whole summer after making a positive impression during a spell at Somerset last season.
"I very much enjoyed my time with the club this year and I am really pleased to be going back," he said.
"Somerset is a special club and it was a pleasure to play for them in 2018. There was a really good atmosphere in the dressing room and there are some very good players at the club. The supporters were excellent and I look forward to seeing everyone again next year.”
Director of cricket Andy Hurry said: "Azhar fitted in seamlessly during his time with us towards the back end of the 2018 season. Knowing the positive impact that he will have both on and off the field, alongside his availability all summer, were key factors in wanting to secure him."
First Published: November 26, 2018, 6:42 PM IST