| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 26. L W Stephens vs H Seidman |
| 0-1 | 30 | 1940 | Ventnor City | A45 Queen's Pawn Game |
| 27. Santasiere vs H Seidman |
 | 0-1 | 65 | 1940 | Ventnor City | A03 Bird's Opening |
| 28. H Seidman vs S Bernstein |
| 0-1 | 32 | 1940 | Ventnor City | B58 Sicilian |
| 29. H Burdge vs H Seidman |
| ½-½ | 14 | 1940 | Ventnor City | B52 Sicilian, Canal-Sokolsky (Rossolimo) Attack |
| 30. H Seidman vs H R Morris |
| ½-½ | 27 | 1940 | Ventnor City | B00 Uncommon King's Pawn Opening |
| 31. H Seidman vs E McCormick |
| 1-0 | 23 | 1940 | Ventnor City | C78 Ruy Lopez |
| 32. M L Hanauer vs H Seidman |
| 1-0 | 28 | 1940 | Ventnor City | A21 English |
| 33. O Ulvestad vs H Seidman |
| ½-½ | 41 | 1940 | Ventnor City | A46 Queen's Pawn Game |
| 34. H Seidman vs P R Geffe |
| 1-0 | 33 | 1940 | Ventnor City | C86 Ruy Lopez, Worrall Attack |
| 35. H Seidman vs Fine |
| 0-1 | 46 | 1941 | Hamilton | C71 Ruy Lopez |
| 36. F Reinfeld vs H Seidman |
 | 0-1 | 35 | 1941 | Marshall CC Championship | E17 Queen's Indian |
| 37. Santasiere vs H Seidman |
| 1-0 | 39 | 1941 | New York State-ch | A04 Reti Opening |
| 38. H Seidman vs Ed Lasker |
| 1-0 | 33 | 1941 | New York State-ch | C86 Ruy Lopez, Worrall Attack |
| 39. H Seidman vs Kashdan |
| 0-1 | 71 | 1941 | New York State-ch | C86 Ruy Lopez, Worrall Attack |
| 40. H Seidman vs Reshevsky |
| 0-1 | 37 | 1942 | United States Championship | C86 Ruy Lopez, Worrall Attack |
| 41. Chernev vs H Seidman |
| 0-1 | 50 | 1942 | United States Championship | D41 Queen's Gambit Declined, Semi-Tarrasch |
| 42. H Seidman vs Kashdan |
| 0-1 | 46 | 1942 | United States Championship | C43 Petrov, Modern Attack |
| 43. I A Horowitz vs H Seidman |
| 1-0 | 27 | 1942 | United States Championship | B03 Alekhine's Defense |
| 44. H Seidman vs Denker |
| 0-1 | 26 | 1942 | United States Championship | A20 English |
| 45. A Pinkus vs H Seidman |
| 1-0 | 46 | 1942 | United States Championship | B02 Alekhine's Defense |
| 46. H Seidman vs H Baker |
| 1-0 | 26 | 1942 | United States Championship | A20 English |
| 47. H Seidman vs Kashdan |
| 0-1 | 55 | 1942 | US Lightning-ch | C80 Ruy Lopez, Open |
| 48. H Seidman vs M Finkelstein |
| 1-0 | 30 | 1944 | Marshall CC-ch (/45) | C59 Two Knights |
| 49. J Araiza Munoz vs H Seidman |
| ½-½ | 52 | 1945 | 1st Pan-American Championship | E18 Queen's Indian, Old Main line, 7.Nc3 |
| 50. H Seidman vs Fine |
| 0-1 | 51 | 1945 | 1st Pan-American Championship | B04 Alekhine's Defense, Modern |
Kibitzing
