Peter Murrell, the chief executive of the SNP, lent the money "to assist with cashflow" after the Holyrood election last year.
Questioned by journalists in the Scottish Parliament, the First Minister would only say it was a “personal contribution” by Mr Murrell.
The Scottish Conservatives previously said it was "beyond odd" for Mr Murrell to be lending his employer a six-figure sum.
The Electoral Commission said the loan was reported late, but it had addressed this by simply providing "guidance to the party", partly due to the SNP's "good compliance record".
Records show the loan of £107,620 was made in June last year. A total of £47,620 was repaid to Mr Murrell in the following months.
The SNP's accounts for 2021 list it as simply "loans from executive management" and state £60,000 remained outstanding at the end of last year. The SNP ended 2021 with a deficit of £751,572, leaving it with reserves of £610,765, down from £1,362,337.
Ms Sturgeon was quizzed about the loan as she exited the Holyrood debating chamber following First Minister’s Questions.
Asked how Mr Murrell was able to give a six-figure loan to the SNP, she said: “He made a personal contribution as a supporter of the party, and that is the position.”
The First Minister was then asked: “If anyone else had come to you and said that the party required a six-figure bailout, and then failed to report it to the Electoral Commission for a year, would they still be chief executive?”
Ms Sturgeon repeated that it was a “personal contribution”. She then attempted to retreat into a lift, before taking the stairs to avoid further questions.
An SNP spokesman previously said: "The loan was reported in our 2021 accounts, which were published by the Electoral Commission in mid-August.
"The nature of this transaction was initially not thought to give rise to a reporting obligation. However, as it had been recorded in the party's 2021 accounts as a loan, it was accordingly then reported to the Electoral Commission as a regulated transaction.
"This was a personal contribution made by the chief executive to assist with cashflow."