Terry Murden, the business editor of The Scotsman and Scotland and Sunday, was convicted after a trial at Edinburgh Sheriff Court that heard he turned up at Nicki Sturzaker's flat uninvited, left unwanted gifts and notes, sent emails, swore and uttered threats towards her.
The 57-year-old was convicted of engaging in a course of conduct that caused her fear and alarm by also contacting her employers and making reference to her in newspaper articles written or edited by him.
Murden, of Mid Steil, Edinburgh, had denied the charges, which related to events between June and October 2013.
But Sheriff Donald Corke told him: "It is clear to me that in the whole circumstances of the case, you have engaged in a course of conduct that caused the complainer to suffer fear and alarm. It is also clear to me that you knew or ought to have known that engaging in that course of conduct would be likely to cause the complainer fear and alarm."
In evidence earlier, Ms Sturzaker said she was employed as a consultant with PR firm The Big Partnership, and was introduced to Murden in 2011 through her work. She said at first their relationship was "purely work", but that had changed about a year later. She ended the relationship in November 2012 but they had remained in contact as friends, she told the court.
In January 2013, Ms Sturzaker said Murden had sent her an email saying he was going to make direct contact with her clients. "I panicked because I felt it was blackmail and would affect my job," she said.
In the next few months she received 15 emails from Murden and contacted the police. She also wrote to Murden and told him she did not want any communication from him.
Asked by Fiscal Depute Arlene Shaw how she felt, Ms Sturzaker replied: "I felt his behaviour was erratic and irrational. He published two articles in one week about my departure from Big Partnership which I thought was an abuse of his position as business editor. He had cost me my job. I felt humiliated."
Despite this, she said, emails and gifts continued to be sent.
She added that Murden could not separate his professional and personal life.
Giving evidence yesterday, Murden said the accusation that he had cost Ms Sturzaker her job was totally unfounded.
Mr Stephenson told the court: "Mr Murden had no idea he was committing an offence. He told the police he was hoping for a reconciliation."
Ms Shaw told the court Murden's actions had a huge impact on Ms Sturzaker's life. "She felt threatened, could not get on with her life.
"She felt the accused was obsessed with her, behaving irrationally and erratically towards her and this had a profound impact on her life".
Sheriff Corke deferred sentence until later this month. Murden's bail was continued.