score of 94 for one to 188 for two by tea.
Dilshan reached his 13th Test century by sweeping left-arm spinner Abdur Rehman for a boundary just before the tea interval and celebrated by raising both hands high in the air.
It was the 35-year-old's first three-figure knock in Test cricket since making a career-best 193 against England at Lord's in June last year.
Dilshan, who hit 13 boundaries and a six, was dismissed in the next over when he was leg-before to off-spinner Saeed Ajmal.
The opener put on 63 for the first wicket with Tharanga Paranavitana and 124 for the second with Sangakkara to lay the foundation for a big first innings total.
Left-handed Sangakkara looked solid with six boundaries, while skipper Mahela Jayawardene was yet to score.
Ajmal was Pakistan's most successful bowler with two for 46 from 15 overs on a slow pitch that offered no assistance to the bowlers after the initial moisture had dried out.
Pakistan's lone success before lunch came midway through the morning session when Paranavitana was stumped in Ajmal's first over after making a scratchy 24.
Paranavitana should have gone on 15 when he was beaten by an Umar Gul delivery, but umpire Ian Gould turned down a loud appeal for a catch at the wicket.
Replays showed a thin edge, but Paranavitana survived because the Umpire Decision Review System (UDRS) is not being used in the series.
The left-hander moved to 24 when he was dropped by Azhar Ali at silly point off Ajmal, but was dismissed later in the same over.
Mohammad Hafeez was leading Pakistan for the first time in Test cricket after Misbah-ul Haq was handed a one-match ban for his team's slow over-rate in Monday's final one-day international.
The tourists awarded a Test cap to 32-year-old middle-order batsman Mohammad Ayub, already a veteran of 93 first-class matches in which he has scored 6,074 runs.
Pakistan picked two seamers, Gul and Junaid Khan, to complement a three-man spin attack of Hafeez, Ajmal and Abdur Rehman.
The hosts were without frontline seamer Chanaka Welegedara, who woke up with a sore shoulder and was replaced by Nuwan Pradeep.