Rotherham stretched their winning sequence to five games with this success at Clifton Lane during a close match in which their forwards defended most effectively.
The Titans have followed up three wins in the British and Irish Cup with two in the Championship and now start preparations for Sunday’s clash at Ashton Gate against league leaders Bristol.
They may not have been at their best in wet and misty conditions, but, importantly, they overcame any weaknesses and went on to claim four points and deprive Pirates of a losing bonus point.
Rotherham stay fourth in the Championship on 22 points behind Bristol, Worcester and London Scottish.
As coach Lee Blackett begins planning his approach for Bristol, arguably the best side in the Championship with seven consecutive wins, he will be without flanker Max Argyle who will find out later today the extent of his foot injury suffered in training before the Pirates match.
On a more positive note, Blackett was delighted with the return of second row forward Barney Maddison, who came on for the last 10 minutes after being out of action for several months with a serious leg injury.
Having Maddison back is a timely boost for Rotherham, especially as there may be some uncertainty as to the availability of second row Sean Robinson who was needed over the weekend by Newcastle Falcons.
A wet ball naturally made handling difficult, but Rotherham still dropped too many passes in the first half, but after an undistinguished opening 40 minutes, they began to deliver.
Tries on 43 and 74 minutes by hooker Tom Cruse and winger Michael Keating took the Titans to an 18-13 lead with six minutes left in a contest that Pirates were unlucky to lose and probably should have won.
However on 64 minutes, outstanding defence by the Titans pack, fighting for survival on their own line with the score at 13-13 forced a penalty; Rotherham prevented what could have been a decisive second try, recovered and 10 minutes later scored through Keating at the other end.
Pirates were then deprived of a losing bonus point as with the last kick of the game, Rotherham fly half James McKinney struck his third penalty in the first minute of injury time.
“Four points against Cornish Pirates is a good result for us,” said Blackett.
“ We put in a good effort but there is plenty to work on. We were not at our best but conditions out there were difficult.
“ We made a lot of errors and Pirates put us under pressure but we showed the right attitude throughout.
“Our forwards, such as Tom Cruse and Ali Birch, did well and I thought Craig Dowsett and James Mitchell who were making their Championship debuts showed a lot of promise.”
Rotherham Titans: Scanlon, Dowsett, Gill, J. Davies, Wilson, McKinney, Mitchell, Hislop, Cruse, Tampin, Parker, Holmes, Rieder, Birch, Ryan.
Replacements: Preece, Williams, Thiede, Maddison, A. Davies, Barrett, Keating.
Scorers: Tries: Cruse, Keating. Conversion: McKinney. Penalties: McKinney 3.
Referee: Andrew Jackson.