Speaking to The Daily Record, Jenkins admitted that she was nervous to appear in 'A Christmas Carol' because she had no previous acting experience.
"When they first called and asked me if I'd like to be in the Christmas special, my first reaction was, 'I can't do it, I'm not an actress'," she said. "I've never trained as an actress. I don't have any experience and that's why I was so nervous about taking on the part."
The Welsh mezzo-soprano suggested that the chance to sing during the on-off episode swayed her to sign on for the role of distressed damsel Abigail Pettigrew.
She explained: "Realising I'd be able to sing too is what swung it for me. When they told me they required singing, I thought, 'Since there's music with my character, I'd love to do it'."
Jenkins further remarked that she is honoured to have appeared in the "iconic show", adding that she hopes to one day show the episode to her grandchildren.
The platinum-selling singer follows on the heels of previous high-profile guest stars such as Catherine Tate, Kylie Minogue and Timothy Dalton who have appeared in the sci-fi series' festive specials.
The Doctor Who one-off episode 'A Christmas Carol' will air on Christmas Day on BBC One in the UK and BBC America in the US.