Smith's effort enabled the hosts to reach 6-259 before play ended early on a weather-affected second day in Manchester on Thursday.
Replying to the Sri Lankans' 236 all out, England were also grateful for 56 from Harry Brook and 42 from Joe Root in between showers that washed out the morning session and then led to the teams walking off the field with more than an hour still to play after tea.
Jamie Smith beats Sri Lanka's Kamindu Mendis with a fine shot at Old Trafford. (AP PHOTO)
Smith, playing in just his fourth Test after being brought in as England's new keeper for this summer, struck knocks of 95 and 70 during the 3-0 series win over the West Indies last month.
Now he has a third Test half-century to his name, after hitting five fours and one six so far so far.Â
The Sri Lankans are still in the match, though, and that's perhaps more than they could have hoped for when reeling on 3-6 after seven overs of day one.
They battled to stay in touch with England, with seam bowler Asitha Fernando claiming figures of 3-68.
Rain meant no play was possible before an early lunch was taken, but England resumed on 0-22 and there was early success for Sri Lanka after two DRS overturns in the space of three balls.
Dan Lawrence successfully reviewed an lbw decision to stay in the middle, only for Sri Lanka to review another lbw call off Fernando that wasn't given against Ben Duckett and get the left-handed opener out for 18.
England stand-in captain Ollie Pope (6) was bowled by the same pacer two overs later, Lawrence edged behind off Vishwa Fernando for 30, and Root then nicked Fernando to wicketkeeper Dinesh Chandimal.
Brook and Smith put on a stand of 62 to steady things, with Brook reaching a half-century for the 13th time in 15 Tests to continue a strong start to his career in the format.
Smith has also taken an immediate liking to the Test arena and carried England past Sri Lanka's total after tea in the first of three five-day contests between the teams.
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