More than 50% of women in advertising have faced sexual harassment at least once in their careers, according to a new study by the American Association of Advertising Agencies.

The trade group’s first study, conducted in June, included 375 responses from women in the advertising field. The findings went beyond just the hot-button issue of harassment to also address broader concerns about gender discrimination.

According to the 4A’s, as the trade group is known, 42% of respondents said there had been times when they were not included in making decisions because of discrimination. Meanwhile, 38% of the women said they experienced times when they were not invited to a high-level meeting when they should have been included.

Nancy Hill, chief executive of the 4As, said its initiative to study the issue of sexual harassment and discrimination comes at a time when recent cases have helped people come forward. Ms. Hill disclosed some of the results of the survey earlier in a story for Campaign US.

“You’ve had several high-profile incidents both with gender and racial discrimination, and people are tired of not talking about it,” Ms. Hill said in an interview. “Now that it’s cracked wide open, people are ready to come forward with stories.”

Just last week, Kevin Roberts, the executive chairman of ad agency Saatchi & Saatchi, resigned after he made comments dismissing the debate over gender diversity on Madison Avenue.

In an interview with Business Insider, Mr. Roberts said the “debate is all over” regarding gender equality in the ad industry and he doesn’t spend “any time” on the issue at his company. The comments drew widespread condemnation in the industry, and Publicis Groupe SA, the parent company of Saatchi & Saatchi where he was also a “head coach,” placed him on leave.

But Ms. Hill thinks the conversation is far from over.

“I think it’s really sad that not only Mr. Roberts but that many people think we are done talking about it,” Ms. Hill said. “We’re not done talking about it.”

Mr. Roberts’ resignation was just one of a series of recent incidents to highlight the lack of gender and racial diversity--and issues with discrimination--in the advertising and marketing industry.

In March, the male chief executive of ad agency J. Walter Thompson was sued by a female subordinate who accused him of an “unending stream of racist and sexist comments, as well as unwanted touching.” Gustavo Martinez, who has denied the allegations, resigned shortly after the lawsuit was filed. JWT and its parent company WPP were also named in the suit and accused of ignoring complaints about the executive’s behavior.

Interpublic Group Cos. in January fired top executive Jim Palmer at Campbell Ewald after it was discovered that an agency employee sent an email inviting colleagues to celebrate “Ghetto Day” with malt liquor, drugs and prostitution.

Ms. Hill said employees at companies with little diversity can struggle to succeed without mentorship.

“Part of the problem we have with the pipeline, even when we get someone hired entry-level, is that there’s no one that looks like them and then they don’t feel that there’s opportunity, and they leave,” Ms. Hill said. “That’s why it’s so important that we get people in the C-suite that are non-white male.”

The 4As said it plans to release more data from its discrimination survey in the fall, which will encompass more than 500 responses, including from men.

Corrections & Amplifications:

The 4A’s fall survey will have more than 500 responses, including responses from men. An earlier version of this article incorrectly stated that the survey would include 500 responses from men.

Write to Cassandra Jaramillo at cassandra.jaramillo@wsj.com