The present paper aims to show the most significant phonetic and morphological features belonging both to the deep Tamian (tāmnieku) subdialects of the Livonic dialect and the Curonian (kursiskās) subdialects of the Middle dialect. The main focus is on the forms used in the deep Tamian subdialects of Pope, Ziras, Piltene, Zlēkas, Ance, Dundaga, and Ugāle, based on the materials acquired by the author during the period 2008–2019, and compared with the data of dialect archive of the Latvian Language Institute of the University of Latvia (collected in the 50s and 60s of the 20th century). In phonetics, a typical feature is the use of broad e, ē, especially in infinitives, e. g., celt ‘to raise, to build’, sēt ‘to sow’, meklēt (Curonian subd.), meklet (Tamian subd.) ‘to search’, the lengthening or diphthongization of short vowels a, e, i, u before consonant r, e. g., dârps ‘work’, ʒērt ‘to drink’, zîrks // ziêrks ‘horse’, bũrt // buõrt ‘to conjure’, palatal consonant ŗ, e. g., kaŗš ‘war’, gaŗš ‘long’, jũŗ ‘sea’, also the use of vowel u before the consonant v or b, e. g., zuve (Curonian subd.), zȗu // zȗi (Tamian subd.) ‘fish’, suvēnc (Curonian subd.), suvēnc // suvans (Tamian subd.) ‘pig’, dubans // dubenc ‘bottom, seat’, dui // dȗv (Tamian subd.) ‘two’, the loss of sounds in different positions, e. g., cilēks (Curonian subd.), cileks (Tamian subd.) ‘human’, ciris (Curonian subd.), cȋrs (Tamian subd.) ‘axe’, dures // duõres (Curonian subd.), dȗrs // dûrs // duôrs (Tamian subd.) ‘the doors’, tēs ‘father’, vẽš ‘wind’, rupš ‘rude’, and assimilation of -ln- to -ll-, e. g., mells ‘black’, vells ‘the devil’, villa (Curonian subd.), vill (Tamian subd.) ‘wool’, pills ‘full’. In morphology, a characteristic feature is the use of ē-stem substantives, e. g., klẽte (Curonian subd.), klẽt (Tamian subd.) ‘barn’, pirte // piêrte (Curonian subd.), pirt // piêrt (Tamian subd.) ‘bathhouse’, sirde // siêrde (Curonian subd.), sȋrd (Tamian subd.) ‘heart’, also the use of archaic plural dative endings -iems or -ems, e. g., zirgiêms // zîrgiêms (Curonian subd.), zirgems // zîrgems (Tamian subd.) ‘for horses’, -ams: mãsams ‘for sisters’, -ems or -ems, e. g., guõvems (Curonian subd.), guõvems (Tamian subd.) ‘for cows’, and the use of prefix / preposition az or āz, e. g., âzvakãr // azvakar (Curonian subd.), azvakar // aizvakar // aîzvakar (Tamian subd.) ‘the day before yesterday’, âz // az kalna (Curonian subd.), az // aiz // aîz kal:n (Tamian subd.) ‘behind the hill’, also prefix or preposition ūz, e. g., ũzlikt (Curonian subd.), ûzlikt (Tamian subd.) ‘to put on’, ûz galda (Curonian subd.), ûz gal:d (Tamian subd.) ‘on the table’, also a typical peculiarity of the Curonian and Tamian subdialects (but not heard nowadays) is the use of pronouns tau, sau ‘for yourself, for myself’.