This was accompanied by four photos - including one of him with actress whose appearance at another session was advertised and livestreamed.
The photo in the Sussex.com post showed him with the actress from the US version of The Office, who appeared in September 2022 on his wife
And Harry's appearance will no doubt draw comparisons to David Brent's character in the UK's original The Office played by who gives a cringeworthy motivational speech to an audience while the song 'Simply the Best' is playing.
The Duke spoke during a 'Beyond Burnout' session at the summit yesterday, where he was joined by Dr Adam Grant, BetterUp's chairman of the 'Center for Purpose and Performance', and Kelly Jones, 'chief people officer' at technology firm Cisco.
No video footage has been released of what Sussex.com referred to as his 'insightful' chat with Dr Grant and Ms Jones. But a post on its website said: 'The trio dove into the psychological toll of leading through uncertainty, sharing personal anecdotes, evidence-based practices, and forward-thinking policies aimed at helping leaders thrive amidst the pressures of today's world and modern corporate life.'
Prince Harry posed with The Office actress Mindy Kaling during his appearance at the 'Beyond Burnout: Transforming C-Level Stress Into Strength' session in San Francisco yesterday
Prince Harry speaks with Kelly Jones, Cisco 'chief people officer', and Dr Adam Grant, BetterUp's chairman of the 'Center for Purpose and Performance', in San Francisco yesterday
Anyone could attend the summit virtually for free by registering online, while in-person tickets at the Hilton Union Square were $1,595 (£1,272) each but sold out.
Does Harry have what it takes to be a royally good life coach?
Fans discussed his appearance in advance and pointed out that the schedule was unclear. One tweeted last week: 'The Uplift conference by BetterUp starts in seven days. We'll probably only see Prince Harry on the last day though. Who knows?'
Another added: 'BetterUp with Prince Harry. In person sold out but attend virtually is still available. Don't miss your chance to enjoy a rare appearance of our fav prince.'
MailOnline has contacted BetterUp and Harry and Meghan's organisation Archewell for comment on why his appearance was not advertised in advance or livestreamed.
His session was called 'Beyond Burnout: Transforming C-Level Stress Into Strength', with the American phrase 'C-level' referring to the most important 'chief' roles at a company such as chief executive, chief operating officer and chief financial officer