A major concern is the impact the general election result will have on the UK's ability to negotiate a good departure deal with the EU in talks that were due to start in just a week's time.
While the negotiations may be delayed as Mrs May attempts to form a minority government – most likely with Northern Ireland's Democratic Unionists, according to reports on Friday – Brexit loomed large in the immediate reactions from top industry figures.
"It's too soon to make any confident predictions but, as many have observed, the business community and uncertainty are unhappy bedfellows … That said, the possibility of more nuanced Brexit negotiations would be welcomed by most in the advertising world," said Paul Bainsfair, Director General of the IPA.
"Whatever the outcome of [the] next few weeks and whatever the makeup of the next government, our political leaders must remember that advertising fuels the economy and that the needs of our industry must be included in Brexit negotiations."
Speaking on behalf of the Advertising Association, its CEO Stephen Woodford warned: "Uncertainty is the word of the day and it will be some time before the full picture emerges. What's clear is that on the biggest political and economic issue of the day – Brexit – the task just got even harder, with the potential for that to crowd out almost anything else.
"UK advertising can play its part in a successful Brexit – but only with the right support. Theresa May's commitment to reducing immigration to the 'tens of thousands' risks damaging our ability to attract the best of global talent and investment."
John Kampfner, Chief Executive of the Creative Industries Federation, told the Drum that Theresa May has now seen that there is no clear mandate for the government to negotiate a "hard Brexit".
"Federation members were 96% in favour of remaining in the EU when surveyed before the referendum. They saw Brexit is a threat to the continued success of the creative industries, damaging growth and the UK’s global outlook. This general election vote now offers the opportunity to look at the issue again," he said.
"The Federation will push for the UK to remain in the single market and the customs union and against undue restrictions on free movement, which we know will damage the capacity of the creative industries to deliver."
Also speaking to the Drum, WPP Chief Executive Sir Martin Sorrell, said: "Now in incredibly uncertain territory with very little, if any, clarity about when, how and what Brexit negotiations will be. Everything is a big question mark. Maybe there will be another election shortly like 1974."
Data sourced from IPA, MediaTel, the Drum; additional content by WARC staff