In synonymy:
Chocorua Crosby & Bishop, 1933 = Diplocephalus Bertkau, 1883 (Hackman, 1954: 28)
Hemistajus Schenkel, 1934 = Diplocephalus Bertkau, 1883 (Thaler, 1970: 256, by transfer of the type species)
Plaesiocraerus Simon, 1884 = Diplocephalus Bertkau, 1883 (Denis, 1949a: 140)
Prosoponcus Simon, 1884 = Diplocephalus Bertkau, 1883 (Simon, 1894a: 656)
Streptosphaenus Simon, 1926 = Diplocephalus Bertkau, 1883 (Denis, 1949a: 140)
Transferred to other genera:
Diplocephalus antepenultimus (O. Pickard-Cambridge, 1882) -- see Tapinocyboides
Diplocephalus buddebergi (Bösenberg, 1899) -- see Thyreosthenius
Diplocephalus cottoni La Touche, 1946 -- see Glyphesis
Diplocephalus curvicervix Denis, 1964 -- see Typhochrestus
Diplocephalus diphyus Heimer, 1987 -- see Dactylopisthes
Diplocephalus fuscipes (Blackwall, 1836) -- see Monocephalus
Diplocephalus fuscipes castaneipes (Simon, 1884) -- see Monocephalus
Diplocephalus leberti (Roewer, 1942) -- see Caracladus
Diplocephalus montanus (Emerton, 1882) -- see Walckenaeria
Diplocephalus pulicarius (Thorell, 1875) -- see Microctenonyx
Diplocephalus pygmaeus (Menge, 1869) -- see Tapinocyboides
Diplocephalus saganus Bösenberg & Strand, 1906 -- see Diplocephaloides
Diplocephalus semiglobosus (Westring, 1861) -- see Entelecara
Diplocephalus tauricus (Thorell, 1875) -- see Styloctetor
Diplocephalus tenellus (Bösenberg, 1899) -- see Tapinocyba
Diplocephalus wamotsus Chamberlin, 1919 -- see Hybauchenidium
Diplocephalus yasudai Saito, 1986 -- see Savignia
In synonymy:
Diplocephalus adjacens O. Pickard-Cambridge, 1904 = Diplocephalus connatus Bertkau, 1889 (Wiehle, 1960a: 496)
Diplocephalus alpinus strandi Kolosváry, 1937 = Diplocephalus alpinus O. Pickard-Cambridge, 1873 (Breitling et al., 2016b: 58)
Diplocephalus arvernus Denis, 1948 = Diplocephalus cristatus Blackwall, 1833 (Bosmans & Oger, 2018: 54)
Diplocephalus bicephalus (Simon, 1884) = Diplocephalus cristatus Blackwall, 1833 (Bosmans & Oger, 2018: 54)
Diplocephalus bicornis (Wider, 1834, T from Lophomma) = Diplocephalus cristatus Blackwall, 1833 (Thorell, 1871a: 108, sub Erigone)
Diplocephalus bihamatus (Menge, 1868, T from Lophocarenum) = Diplocephalus latifrons O. Pickard-Cambridge, 1863 (Thorell, 1871a: 107, sub Erigone)
Diplocephalus brunneus (Bösenberg, 1902, T from Araeoncus) = Diplocephalus permixtus O. Pickard-Cambridge, 1871 (Tullgren, 1955: 328)
Diplocephalus caespitum (C. L. Koch, 1841, T from Micryphantes) = Diplocephalus cristatus Blackwall, 1833 (Thorell, 1871a: 108, sub Erigone)
Diplocephalus connectens Kulczyński, 1894 = Diplocephalus alpinus O. Pickard-Cambridge, 1873 (Thaler, 1995b: D479, sub D. connectens)
Diplocephalus cristatus angusticeps Holm, 1973 = Diplocephalus cristatus Blackwall, 1833 (Tanasevitch, 2011c: 138)
Diplocephalus cuneatus (Emerton, 1909) = Diplocephalus subrostratus O. Pickard-Cambridge, 1873 (Eskov, 1988c: 23)
Diplocephalus dimidiatus (Denis, 1945) = Diplocephalus graecus O. Pickard-Cambridge, 1873 (Denis, 1964c: 63)
Diplocephalus eborodunensis (O. Pickard-Cambridge, 1875) = Diplocephalus helleri L. Koch, 1869 (Simon, 1926: 497, sub Plaesiocraerus)
Diplocephalus foraminifer (O. Pickard-Cambridge, 1875) = Diplocephalus cristatus Blackwall, 1833 (Bosmans & Oger, 2018: 54)
Diplocephalus foraminifer thyrsiger (Simon, 1884) = Diplocephalus cristatus Blackwall, 1833 (Bosmans & Oger, 2018: 54)
Diplocephalus incertus (L. Koch, 1879, T from Erigone) = Diplocephalus barbiger Roewer, 1955 (Holm, 1970: 191, sub D. barbatus)
Diplocephalus maculifrons Kulczyński, 1926 = Diplocephalus subrostratus O. Pickard-Cambridge, 1873 (Eskov, 1988c: 23)
Diplocephalus meticulosus (Simon, 1918, T from Entelecara) = Diplocephalus picinus Blackwall, 1841 (Denis, 1949a: 136)
Diplocephalus morum (O. Pickard-Cambridge, 1894, T from Gongylidium) = Diplocephalus picinus Blackwall, 1841 (O. Pickard-Cambridge, 1911b: 53)
Diplocephalus nuncius (Simon, 1882, T from Erigone) = Diplocephalus graecus O. Pickard-Cambridge, 1873 (Simon, 1926: 512, sub Entelecara)
Diplocephalus obtusus Denis, 1952 = Diplocephalus helleri L. Koch, 1869 (Georgescu, 1969a: 204)
Diplocephalus opacithorax (Simon, 1884) = Diplocephalus latifrons O. Pickard-Cambridge, 1863 (Simon, 1926: 380, sub Plaesiocraerus)
Diplocephalus picinus humiliceps (Denis, 1945) = Diplocephalus picinus Blackwall, 1841 (Wiehle, 1960a: 515)
Diplocephalus rectilobus (Simon, 1884) = Diplocephalus cristatus Blackwall, 1833 (Bosmans & Oger, 2018: 54)
Diplocephalus sabulicola Bosmans, 1996 = Diplocephalus mystacinus Simon, 1884 (Bosmans, 2002: 22)
Diplocephalus spinosus Hull, 1901 = Diplocephalus permixtus O. Pickard-Cambridge, 1871 (Jackson, 1907b: 404)
Diplocephalus tatricus (Kulczyński, 1882, T from Erigone) = Diplocephalus helleri L. Koch, 1869 (Simon, 1884a: 755, sub Plaesiocraerus)
Homonyms replaced:
Diplocephalus barbatus (L. Koch, 1879) -- see Diplocephalus barbiger Roewer, 1955 Roewer, 1955c
Diplocephalus montanus Tanasevitch, 1989 -- see Diplocephalus montaneus Tanasevitch, 1992
Nomina dubia:
Diplocephalus alpinus subrufus Roșca, 1935: 245, f. 5-6 (mf, Romania) -- Fedoriak, Voloshyn & Moscaliuc, 2016: 86
Diplocephalus coniceps Strand, 1906b: 616 (m, Somalia) -- Scharff, 1990b: 144
Diplocephalus fallaciosus (Bertkau, in Förster & Bertkau, 1883: 229, pl. 3, f. 2, m, Germany, originally in Lophocarenum) -- Wiehle, 1960a: 514
Diplocephalus pullinus Simon, 1918b: 153 (m, France) -- Lecigne et al., 2022: 14