The wrestler-turned-actor could charge advertisers more than $1m (£790,000) per post last year, according to the tech firm Hopper HQ.
The Fast and Furious star knocked socialite Kylie Jenner off the top spot as her earnings fell.
She has 182 million Instagram followers, while he has 187 million.
To work out a celebrity's worth on the social media platform, Hopper HQ looks at the number of followers they have, and the level of engagement on their posts, such as likes or comments.
It does not, however, give figures for the amount of revenue generated by stars on the platform.
Other high value personalities on its list for 2019 included footballer Cristiano Ronaldo, who was worth $889,000 per post, and socialite Kim Kardashian, who could charge $858,000.
Earlier this year, Dwayne "The Rock" Johnson was crowned by Forbes as the highest-paid actor in the world, having earned nearly $90m last year before tax.
Outside of his film work, the action star has a major commercial partnership with Under Armour, the US sports brand he signed with in 2016.
He has also been sponsored by tech giant Apple and the Norwegian bottled water brand Voss, in which he holds a stake.
However, his current list of endorsement deals on Instagram appears surprisingly short.
Scrolling through is feed, aside from selfies of the muscle-bound actor working out, most of The Rock's recent posts promote his own Tequila brand, Teremana.
Other than that, his promotional posts are largely for new episodes of The Titans, an NBC TV series which he hosts, or films in which he stars, such as upcoming DC Comics feature Black Adam.
1. Dwayne 'The Rock' Johnson, 187m followers - just over $1m per post
2. Kylie Jenner, 182m followers - $986,000 per post
3. Footballer Cristiano Ronaldo, 225m followers - $889,000 per post
4. Socialite Kim Kardashian, 176m followers - $858,000 per post
5. Pop star Ariana Grande, 191m followers - $853,000 per post
6. Actress and singer Selena Gomez, 180m followers - $848,000 per post
7. Pop star Beyoncé Knowles, 149m followers - $770,000 per post
8. Pop star Justin Bieber, 139m followers - $747,000 per post
9. Pop star Taylor Swift, 135m followers - $722,000 per post
10. Footballer Neymar da Silva Santos Junior, 139m followers - $704,000 per post
"Dwayne 'The Rock' Johnson has had an incredible year as he continues to dominate Hollywood with blockbuster hits, including Fast & Furious and the second Jumanji film," said Mike Bandar, co-founder of Hopper HQ.
"It was particularly interesting to see the star rise in Instagram fame this year as he moved up six places in the list and overtook reigning champion Kylie Jenner."
In May, Forbes magazine removed reality TV star and cosmetics entrepreneur Kylie Jenner from its list of billionaires, accusing her family of inflating the value of her makeup business.
This year was the first time in four years in which a Jenner or Kardashian wasn't top of Hopper HQ's Instagram celebrity rich list.