Mathews was 87 not out as he approached his second Test hundred and in company of Dinesh Chandimal (89) added an invaluable 138-run partnership for the fifth wicket to leave Pakistani bowlers frustrated in the first session.
At tea the other unbeaten batsman was Prasanna Jayawardene with 14 as Sri Lanka, who trailed by 179 runs in the first innings, now lead by 176 runs with five wickets intact.
Mathews, who made 91 in the first innings, has so far hit nine boundaries and a six off 211-ball knock.
But both Mathews and Chandimal were not bothered at all and even the second new ball, taken at 249-4, failed to benefit Pakistan with a wicket as Sri Lanka reached 285-4 at lunch, adding 99 to their overnight score of 186-4.
Also Read
Chandimal glanced off-spinner Saeed Ajmal for his seventh boundary to reach his fifth Test half-century off 79 balls.
Mathews was more aggressive, hitting Ajmal for a six early in the day and then took a single off the same bowler to reach his 12th fifty -- and second in the match following his 91 in Sri Lanka's first innings of 204.