The route, launched in March, will gain an extra 2.50pm departure, in addition to existing 6.50am and 5.55pm services.
Return flights are fixed for 8.50am, 4.40pm and 7.50pm respectively.
Loganair is also operating one Saturday morning flight, and two on Sundays.
Fares lead in from £69.99pp one-way.
Onward flights from Heathrow with British Airways, KLM, Air France, Emirates, Turkish Airlines, United Airlines and Qatar Airways are available to Tees Valley passengers through Loganair’s interline agreements.
It comes after Loganair returned to Teesside International last November after a two-and-a-half year absence.
Tees Valley mayor Ben Houchen said: “It’s fantastic Loganair is adding more services to help our local people get to London either for business or pleasure, get a connection abroad as international travel guidelines continue to be reviewed, and to show people from the capital what Teesside has to offer."
