A former aide to Hillary Rodham Clinton who helped set up the server that housed Mrs. Clinton’s private email account plans to invoke his Fifth Amendment right in response to congressional questions about the email practices, according to two people who have been briefed on the matter.

The former aide, Bryan Pagliano, was subpoenaed to testify before a House committee, but a lawyer for Mr. Pagliano has told the panel that his client will assert his right to remain silent and decline to answer their questions.

The subpoena was issued by the House committee investigating the 2012 attacks in Benghazi, Libya. As part of its inquiry, the panel is examining Mrs. Clinton’s use of a private email account while she was secretary of state, which shielded her correspondences from congressional inquiries.

Mr. Pagliano was the information technology director for Mrs. Clinton’s 2008 presidential campaign and then worked at the State Department as an adviser and special projects manager for its chief technology officer, according to his LinkedIn page. He left the State Department in February 2013, the same month Mrs. Clinton stepped down as secretary of state.

It is not clear why Mr. Pagliano is refusing to answer questions about the server. The F.B.I. is investigating how classified information was handled in connection with the account, but no evidence has surfaced that Mr. Pagliano had anything to do with those materials.

Mr. Pagliano’s lawyer, Mark MacDougall, declined to comment.

A Clinton campaign aide said that Mr. Pagliano’s decision was “both understandable and disappointing to us, because we believe he has every reason to be transparent about his I.T. assistance.”

“We had hoped Bryan would also agree to answer any questions from the committee and had recently encouraged him to grant the committee’s request for an interview,” the aide said.

The aide added: “Bryan is an utter professional and a wonderful young man who does not live in the public eye and understandably may not wish to be drawn into a political spectacle.”

The Republican-controlled committee had planned to call Mr. Pagliano to testify behind closed doors, similar to the way it has interviewed some top aides to Mrs. Clinton and Americans who were in Benghazi.

Even if Mr. Pagliano does not back down, the panel will probably still call him to testify and force him to invoke the Fifth Amendment in person.

Mr. Pagliano’s response to the subpoena was first reported by The Washington Post

Mrs. Clinton’s longtime lawyer and adviser, Cheryl Mills, is scheduled to testify before the committee on Thursday. The panel wants to ask her about how the email account was set up and how Mrs. Clinton decided which emails she should hand over to the State Department in response to its request last year for government records from the account.

Nick Merrill, a spokesman for Mrs. Clinton, “had made every effort to answer questions and be as helpful as possible and has encouraged her aides, current and former, to do the same, including Bryan Pagliano.”

“In fact, two of those aides are due to testify this week, and she is eager to testify in a public hearing in October,” Mr. Merrill said.

The ranking Democratic member of the House committee, Representative Elijah E. Cummings of Maryland, defended Mr. Pagliano’s decision.

“Although multiple legal experts agree there is no evidence of criminal activity, it is certainly understandable that this witness’s attorneys advised him to assert his Fifth Amendment rights, especially given the onslaught of wild and unsubstantiated accusations by Republican presidential candidates, members of Congress and others based on false leaks about the investigation,” Mr. Cummings said.

“Their insatiable desire to derail Secretary Clinton’s presidential campaign at all costs has real consequences for any serious congressional effort,” he added.