On January 10, 2018, the Huffington Post published an allegation from former Klein staffer Erica Vladimer that Klein had forcibly kissed her outside a bar in March 2015. State Sen. Diane Savino (D), another IDC member who was dating Klein at the time, was also present. Klein and Savino held a conference call on January 10 where they denied that the incident happened. Klein's lawyer, Michael Zweig, said the following: "...it simply defies credibility and reason to suggest that Sen. Klein would have, in full view of both his longtime girlfriend, numerous staff members, and in the middle of a very visible and public street, assault Ms. Vladimir, as her allegation inaccurately suggest." Klein invited the Joint Commission on Public Ethics (JCOPE) to investigate the case in January 2018. In December 2019, JCOPE announced it was opening an investigation into the allegations against Klein. On June 8, 2020, JCOPE hearing officer Richard Rifkin filed his report on the allegations of Klein's misconduct. Rifkin concluded that the allegations against Klein were outside the commission's authority since they didn't involve government decision-making. The commission voted in August to overrule Rifkin's decision and order him to conduct a hearing into whether the allegations were true or not. Klein filed a lawsuit in the state Supreme Court on December 21, 2020, calling for the JCOPE investigation's dismissal.

See also: Sexual assault and harassment in American politics (2017-2018) Jeffrey Klein was mentioned during a wave of sexual assault and misconduct allegations in 2017 and 2018. On January 10, 2018, the Huffington Post published an allegation from former Klein staffer Erica Vladimer that Klein had forcibly kissed her outside a bar in March 2015. State Sen. Diane Savino (D), another IDC member who was dating Klein at the time, was also present. Klein and Savino held a conference call on January 10 where they denied that the incident happened. Klein's lawyer, Michael Zweig, said the following: "...it simply defies credibility and reason to suggest that Sen. Klein would have, in full view of both his longtime girlfriend, numerous staff members, and in the middle of a very visible and public street, assault Ms. Vladimir, as her allegation inaccurately suggest." Klein invited the Joint Commission on Public Ethics to investigate the case.