Samantha and Simon Hardman from Sheffield, and their 8-month-old daughter Emily, were also presented with a painting of Bodnant to mark the occasion.
The National Trust's Grade I listed garden near Conwy in North Wales reached its milestone in a blaze of autumn colour, months ahead of target.
The Hardmans were visiting the 140-year-old garden for the first time on the recommendation of a relative.
They said: "We were expecting a beautiful garden, but we were definitely not anticipating the shower of confetti, the huge cake, the bubbly and the crowd of staff, volunteers and visitors that greeted our arrival! This was our first ever visit to Bodnant Garden, but it won't be our last – the garden is absolutely magnificent, and the autumn colours are stunning. We will be back, and we'll be recommending it to all our friends."
Bodnant Garden was founded in 1874 by Victorian industrial chemist and entrepreneur Henry Pochin. It has since been developed by five generations of his family, in conjunction with the National Trust since 1949.
The garden has attracted around 180,000 visitors per year for some years - regularly welcoming around 50,000 in May alone who flock to see the famous Laburnum Arch, the UK's oldest and longest pergola walkway.
Visitor numbers have been steadily rising since 2013 with the opening of the Winter Garden, Old Park meadow, Yew Dell and Far End lakeside garden.
General manager William Greenwood said 200,000 visitors was "a bit like our own 4-minute mile".
"We've knocked on the door before but never gone through. Now we've sprinted across the line and I'm convinced that we're going to see more visitors as the garden gets better and bigger year by year.
"An absolutely amazing achievement and a stunning tribute to so much hard work and dedication in all weathers from our hardworking staff and volunteer team. I can't thank enough every single one of them."