She was diagnosed with leukemia in late July 2016. Her close friend Jan Christian Mollestad contacted Cohen to tell him Ihlen was dying. Leonard Cohen penned a poignant final letter to her writing:

Well Marianne it’s come to this time when we are really so old and our bodies are falling apart and I think I will follow you very soon. Know that I am so close behind you that if you stretch out your hand, I think you can reach mine. And you know that I’ve always loved you for your beauty and your wisdom, but I don’t need to say anything more about that because you know all about that. But now, I just want to wish you a very good journey. Goodbye old friend. Endless love, see you down the road.

— Leonard Cohen, [7]

She died aged 81 on 28 July 2016, in Oslo.[8] Cohen followed her shortly after, dying on 10 November 2016